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Robert Stewart, PhD (Nacogdoches, TX), is a retired U.S. Army officer
and currently Associate Professor of Biology and Director of the
Biotechnology Division at Stephen F. Austin State University.

Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights

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 CONTENTS

Introduction

Chapter 1 Enzymes and Metabolism

Questions 1–24

Chapter 2 DNA and Protein Synthesis

Questions 25–64

Chapter 3 The Molecular Biology of Eukaryotes

Questions 65–89

Chapter 4 Microbiology
Questions 90–136

Chapter 5 The Eukaryotic Cell

Questions 137–181

Chapter 6 Specialized Cells and Tissues

Questions 182–224

Chapter 7 The Nervous and Endocrine Systems

Questions 225–265

Chapter 8 The Circulatory, Lymphatic, and Immune Systems

Questions 266–310

Chapter 9 The Digestive and Excretory Systems

Questions 311–344

Chapter 10 The Muscle and Skeletal Systems

Questions 345–370

Chapter 11 The Respiratory System

Questions 371–391
Chapter 12 The Skin
Questions 392–411

Chapter 13 The Reproductive System and Development

Questions 412–435

Chapter 14 Genetics
Questions 436–478

Chapter 15 Evolution
Questions 479–500

Answers
 INTRODUCTION

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 CHAPTER 1

Enzymes and Metabolism

1. Bacteria are capable of producing 38 net molecules of adenosine

triphosphate (ATP) from every molecule of glucose fully metabolized
by oxidative phosphorylation. Which of the following is NOT true
about this statement?
(A) The majority of the ATP molecules are produced within the
mitochondria.
(B) This yield is greater than that produced from a molecule of glucose
within a human cell.
(C) This total yield of ATP includes molecules produced by substrate-
level phosphorylation.
(D) The presence of oxygen is required to produce this total yield of
ATP.
(E) This yield includes ATP expenses required to drive glycolysis
forward.

2. The maximum activity of any enzyme from a halophilic bacterium

would be found at
(A) a pH nearer 7.4 than 4.2
(B) a temperature closer to 25°C than 35°C
(C) a salt concentration closer to 5 percent than 0.85 percent
(D) a pH nearer 4.2 than 7.4
(E) any temperature exceeding 45°C

3. Which of the following is a five-carbon molecule involved in the TCA

cycle?
(A) α-ketoglutarate
(B) Oxaloacetate
 (C) Acetyl CoA
(D) Pyruvate
(E) Succinyl CoA

4. The breakdown of glucose to pyruvate by a cell is an example of a(n)

(A) anabolic reaction
(B) aerobic reaction
(C) synthetic reaction
(D) catabolic reaction
(E) β-oxidation reaction

5. The ultimate net H2O production resulting from the introduction of a

single molecule of acetyl CoA into the TCA cycle is
(A) 2 molecules
(B) 4 molecules
(C) 0 molecules
(D) 1 molecule
(E) 11 molecules

6. The site on an enzyme that will bind the substrate is called the
(A) prosthetic group
(B) active site
(C) allosteric site
(D) reactive group
(E) dehydration site

7. The sequential process of producing acetyl CoA from long-chain fatty

acids is known as
(A) hydrogenation
(B) oxidative phosphorylation
(C) β-oxidation
(D) sequential reduction
(E) dehydrogenation
 8. An enzyme is active in the stomach of an animal but quickly loses its
activity when it leaves the stomach. This example illustrates that
enzymes are
(A) specific to the organs in which they are produced
(B) inactivated by movement
(C) inhibited by excessive substrate in the small intestine
(D) sensitive to changes in pH
(E) inhibited by changes in temperature

9. Any reaction that releases energy is referred to as

(A) catabolic
(B) metabolic
(C) glycolytic
(D) glycolysis
(E) anabolic

10. Which of the following is NOT a product of the TCA cycle?

(A) CO2
(B) ATP
(C) NADH
(D) Acetyl CoA
(E) FADH2

11. When NADH is converted to NAD, the process is categorized as

(A) dehydration
(B) oxidation
(C) catalysis
(D) reduction
(E) exergonic

12. Homeostasis, the steady-state battle against entropy so vital to life, is

possible for cells because
(A) cells cannot convert energy from one form to another
 (B) all cells are autotrophic
(C) cells continually take up energy from the environment
(D) all cellular reactions are anabolic
(E) all cellular reactions are exergonic

13. Which of the following has catalytic properties?

(A) Carboxypeptidase A
(B) Iron
(C) Histidine
(D) ATP
(E) N-acetylmuramic acid

14. The activity of an enzyme can be controlled by various conditions and

factors. Which of the following is a substance that halts enzyme
activity by binding irreversibly to the enzyme?
(A) An inactivator
(B) A cofactor
(C) A coenzyme
(D) A repressor
(E) A metabolic poison

15. Energy is important to all forms of life because

(A) all forms of life require a continuous supply of it
(B) it is required to do work
(C) it is required to make specific alterations in the cell
(D) all of the above
(E) both A and B only

16. How many enzymatic steps are involved in converting glucose to

pyruvate through the process of glycolysis?
(A) 3
(B) 5
(C) 8
(D) 10
 (E) 12

17. Photosynthesis is an important process that

(A) is performed by heterotrophs
(B) produces oxidized products
(C) uses H2O and CO2 as reactants
(D) only plants can perform
(E) is performed by organisms living near deep-sea thermal vents

18. A competitive inhibitor

(A) binds at a site other than the active site
(B) cannot be processed by the enzyme
(C) irreversibly binds and inactivates the enzyme
(D) does not inhibit enzyme activity but lowers substrate concentration
(E) binds to and inactivates the substrate

19. Which of the following components of the mitochondrial electron

transport system transfers protons and electrons?
(A) Coenzyme Q
(B) Cytochrome a
(C) Cytochrome c
(D) ATP synthase
(E) Cytochrome cl

20. A person with a bacterial infection usually develops a fever. This fever
helps protect the person by inhibiting the growth of bacteria because
(A) bacteria reproduce more rapidly at higher body temperatures
(B) fever blocks the synthesis of proteins in bacteria
(C) the higher temperature increases the metabolic rate of bacteria
(D) sweating removes cofactors, required by bacteria, from the blood
(E) enzymes do not function as well at a temperature that is not
optimal
21. Which of the following would NOT be used as a final electron
acceptor in anaerobic respiration?
(A) Sulfur
(B) Protons
(C) Iron
(D) Nitrogen
(E) Oxygen

22. The respiration process that results in the buildup of organic

compounds in a cell is known as
(A) dehydration
(B) fermentation
(C) reduction
(D) anaerobiosis
(E) oxidation

23. If a small molecule that acts as a substrate for a specific enzyme were
modified by being coupled to a larger molecule before the reaction
could occur, what would be the most likely result?
(A) The reaction catalyzed by the enzyme would progress in the
normal fashion because the part of the molecule that interacts with
the enzyme would remain substantially unchanged.
(B) The rate of the reaction would increase because of the additional
mass of the reactant.
(C) The rate of the reaction would increase because the additional
molecular structure would act as a cofactor.
(D) The enzyme would be permanently disabled by the larger portion
of the substrate molecule.
(E) The enzyme would not be able to interact with the modified
substrate.

24. If 6.5 g of a protein were fully oxidized, what would be the net energy
released for use by a body?
(A) 36 kilocalories
(B) 114 kilocalories
(C) 26 kilocalories
(D) 58.5 kilocalories
(E) 6.5 kilocalories
 CHAPTER 2

DNA and Protein Synthesis

25. Which of the following elements is NOT required for a cell to

synthesize DNA?
(A) Phosphorus
(B) Nitrogen
(C) Hydrogen
(D) Carbon
(E) Iron

26. Which of the following DNA sequences is least likely to represent a

restriction endonuclease cut site?
(A) AGCT
(B) GACGAC
(C) GGATCC
(D) AAGCTT
(E) GATATC

27. In genetic engineering the term sticky ends refers to

(A) the effects on mRNA following posttranscriptional modification
within the nucleus
(B) the results on DNA following the work of the DNA replisome
(C) the product produced by most restriction enzymes
(D) the physiological changes produced by an inversion mutation
(E) the increased production of glycolipids following induction of the
glucose operon

28. DNA ligase is used to

 (A) initiate DNA synthesis in prokaryotes
(B) stabilize the DNA helix to prevent supercoiling during DNA
replication
(C) identify the site on an operon where RNA polymerase binds to the
DNA helix
(D) join together Okazaki fragments during lagging-strand DNA
synthesis
(E) initiate DNA synthesis in eukaryotes

29. Referring to the preceding figure, if the base sequence triplet AAC
were found on the DNA sense strand, what would be the resulting
amino acid added within the ribosome?
(A) Leucine
 (B) Asparagine
(C) Proline
(D) None (It codes for a halt to protein synthesis.)
(E) Glycine

30. If a mutation resulted in a single base substitution at the third position

within the anticodon region of tRNA, what would be the most likely
result?
(A) It would make no difference to the cell because redundancy in the
genetic code would prevent a change in the resulting protein.
(B) The resulting protein would most likely be dysfunctional.
(C) The chances are good that the resulting protein would remain
unchanged because of the redundancy within the genetic code.
(D) The change would only affect the resulting protein if it resided
within an enzyme’s active site.
(E) Such a change within an anticodon region always has a lethal
effect on the cell.

31. Which enzyme is critical to the process referred to as PCR?

(A) DNA ligase
(B) RNA polymerase
(C) Reverse transcriptase
(D) DNA polymerase
(E) DNA gyrase

32. Which of the following is the proper representation for the process
known as biology’s central dogma?
(A) RNA ← DNA → proteins
(B) Replication → transcription → translation
(C) Genotype changes produce phenotype changes
(D) Survival of the fittest results in the founding of new species
(E) RNA → DNA → RNA → proteins

33. Molecular biologists can identify an open reading frame by the

 (A) postpromotor presence of the triplet TAC on the sense strand
(B) presence of the triplet AUG in the promoter region
(C) presence of the conserved sequence TATA in eukaryotic DNA
(D) presence of the polyA tail
(E) presence of the conserved sequence TATAAT in the operator
region of prokaryotes

34. The term 60S should immediately bring to mind the

(A) large ribosomal subunit of prokaryotes
(B) intact eukaryotic ribosome
(C) entire structure responsible for cellular translation
(D) structure of the spliceosomes within the eukaryotic nucleus
(E) large ribosomal subunit of eukaryotes

35. Which of the following mutations is most likely to produce a lethal

condition?
(A) A point substitution within the region coding for the leader
segment of the mRNA coding for a critical enzyme
(B) An inversion within a region coding for an intron within the
mRNA coding for a critical enzyme
(C) A point substitution within the TATAAT box within the promoter
for the gene coding for a critical enzyme
(D) A frameshift mutation within a region coding for an intron within
the mRNA coding for a noncritical enzyme
(E) A silent mutation within a gene coding for a critical enzyme

36. Which of the following enzymes was discovered as a result of research

into why bacteria could survive infections with bacteriophages?
(A) β-lactamase
(B) DNA ligase
(C) DNA-dependent RNA polymerase
(D) RNA-dependent DNA polymerase
(E) Restriction endonuclease
37. Bacterial transcription requires the presence of what is known as a
sigma subunit. Why is this component important?
(A) It must be present to locate the polyA tail properly.
(B) It must be present for the RNA polymerase to locate the promoter
region properly.
(C) It must be present to ligate the Okazaki fragments properly.
(D) It is required to terminate the process of transcription properly.
(E) It is required as a cofactor of the RNA polymerase and must be
present throughout the process to maintain transcription.

38. DNA-dependent RNA polymerase functions only within the

(A) nucleus and ribosomes
(B) nucleus
(C) nucleus, mitochondria, and ribosomes
(D) nucleus, mitochondria, and chloroplasts
(E) mitochondria and chloroplasts

39. Where are ribosomes found within a cell?

(A) Only within the cytoplasm
(B) Within the cytoplasm and endoplasmic reticulum
(C) Within the cytoplasm, mitochondria, and chloroplasts
(D) Only within the nucleus
(E) Only within the endoplasmic reticulum

40. Which of the following is the best distinction between DNA and
RNA?
(A) Base pairing only occurs in DNA.
(B) Adenine forms base pairs with uracil in DNA but with thymidine
in RNA.
(C) The sugar-phosphate-sugar-phosphate repeating backbone
structure is found only in DNA.
(D) The backbone in RNA contains fewer oxygen atoms than that
found in DNA.
(E) Only DNA is found in the eukaryotic nucleus.
41. All of the following enzymes are required for DNA replication
EXCEPT
(A) endonuclease
(B) ligase
(C) DNA polymerase
(D) topoisomerase
(E) helicase

42. Ribosomes are responsible for what cellular activity?

(A) Translation
(B) Glycosylation and assembly of proteins
(C) Polyadenylation
(D) Reverse transcription
(E) Posttranscriptional modification

43. A frameshift mutation within a region coding for an intron would

(A) result in the cell’s death because all genes coded downstream
would be affected
(B) result in the cell’s death because no RNA polymerase binding site
found downstream would be recognizable
(C) have no real effect on the cell because the frameshift would be
corrected during transcription
(D) result in the cell’s death because the resulting message could not
be translated
(E) have no real effect on the cell because the intron would still be
spliced out properly

44. Which of the following codon pairs would most likely code for the
same amino acid because of the wobble in the genetic code?
(A) AAC and ACC
(B) UUU and UUA
(C) UUA and CUA
(D) GGG and CCC
(E) CAU and UAC
45. The phases of translation consist of
(A) initiation and translation
(B) initiation, elongation, and termination
(C) elongation, continuation, and termination
(D) initiation, elongation, modification, and termination
(E) initiation and termination

46. Which of the following sequences would hybridize most strongly to

the sequence 5′ -ATTTGGGCCAATGGGCCCTTTAA-3′?
(A) 5′-ATTTGGGCCAATGGGCCCTTTAA-3′
(B) 3′-ATTTGGGCCAATGGGCCCTTTAA-5′
(C) 3′-TATTCCCGGTTACCCGGGAAATT-5′
(D) 5′-TATTCCCGGTTACCCGGGAAATT-3′
(E) 3′-TAAACCCCCAATCCCGGGAAATT-5′

47. Ultraviolet light is carcinogenic because

(A) it produces thymidine dimers that interfere with DNA replication
and cell control
(B) it causes base pairing mismatches that interfere with DNA
replication
(C) it produces massive amounts of degraded DNA that prevents the
replication of exposed cells
(D) it produces massive amounts of degraded DNA that destroys the
ability to control cell growth
(E) it produces inversion mutations that interfere with cellular control

48. When comparing the structure of bacterial and eukaryotic DNA, it is

observed that
(A) bacterial DNA is thinner and less complex
(B) bacterial DNA contains uracil instead of thymidine
(C) bacterial and eukaryotic DNA are identical in structure
(D) bacterial DNA is interpreted with a different genetic code than
eukaryotes
(E) bacterial DNA is constructed with ribose rather than deoxyribose
49. The Shine-Dalgarno sequence is recognizable by a
(A) ribosome
(B) replisome
(C) restriction endonuclease
(D) spliceosome
(E) sigma factor

50. RNA is believed to be a more primitive molecule than DNA because

(A) it is more flexible in structure
(B) it uses a less complex base pairing system
(C) it lacks the base pairing system used by DNA
(D) it can have catalytic properties
(E) it is always a much shorter molecule than DNA

51. Intact ribosomes are assembled

(A) within the nucleolus of the cell
(B) at the nuclear pores of the cell
(C) at the location of transcription in eukaryotes
(D) within the Golgi bodies of eukaryotes
(E) within the cytoplasm of the cell

52. Which of the following increases fidelity during replication?

(A) SOS repair
(B) Excision repair
(C) Photoreactivation of thymidine dimers
(D) Recombination repair
(E) Exonuclease proofreading

53. Which of the following is true concerning a nonsense mutation?

(A) It never produces a lethal effect.
(B) It can be repaired by photoreactivation.
(C) It always produces a lethal effect.
(D) It is equivalent to the term missense mutation.
 (E) It would have no effect on a cell if it were present within an intron.

54. If a nucleic acid were found in a cell with a long terminal repetitive
sequence of adenines, it would probably be
(A) synthetic and inserted by researchers
(B) mRNA
(C) cDNA
(D) a waste product of posttranscriptional modification
(E) rDNA with the repetitive sequence representing the last exon

55. What enzyme(s) is (are) used by researchers to excise genes of

interest?
(A) DNA-dependent RNA polymerase
(B) DNA-dependent DNA polymerase
(C) DNA ligase and primase
(D) Restriction endonucleases
(E) RNA-dependent RNA polymerase

56. Which base pairing represents the strongest binding?

(A) A · T
(B) C · A
(C) G · T
(D) G · C
(E) A · U

57. The function of which of the following is used in lagging-strand

synthesis but not leading-strand synthesis?
(A) DNA ligase
(B) Helicase
(C) Topoisomerase
(D) DNA-dependent DNA polymerase
(E) Sigma factor
58. The sequence found in eukaryotes that is analogous to that of the
Pribnow box found in prokaryotes is
(A) TAATAT
(B) TATAAT
(C) TATA
(D) TAAT
(E) ATAT

59. The expression “replication is semiconservative” means that

(A) DNA replicates in a more effective manner than RNA does
(B) one original strand base paired to one newly synthesized strand is
the result of replication
(C) DNA replicates in a more efficient manner than RNA does
(D) following replication, one copy is composed of only newly
synthesized DNA, while the other contains the original template
strands
(E) both copies of DNA following replication are almost, but not quite,
exact copies of the originals

60. Which of the following mechanisms of DNA repair is mediated by the

recA protein?
(A) Exonuclease proofreading
(B) Photoreactivation
(C) SOS repair
(D) Excision repair
(E) Recombination repair

61. Which of the following statements regarding tRNA, rRNA and mRNA
is NOT true?
(A) They are all synthesized within the nucleus in eukaryotes.
(B) They all contain uracil in lieu of thymine.
(C) They are all present during translation.
(D) They can all form short, complementary double-stranded regions
with each other.
 (E) They all code for the production of some protein product.

62. During PCR, what mechanism is used to separate the complementary

DNA strands from each other?
(A) Heating
(B) The melting capability of DNA polymerase
(C) The inclusion of bacterial ribosomes
(D) The inclusion of restriction endonucleases
(E) The addition of large amounts of sodium chloride

63. To isolate genes for cloning into another organism, DNA is frequently
fragmented by enzymes. To purify these fragments, what is done next?
(A) The fragments are separated by gradient ultracentrifugation.
(B) The desired fragments are removed from the solution by affinity
chromatography.
(C) The various fragments are separated from each other by agarose
gel electrophoresis.
(D) The fragments are separated from each other by a series of
filtration steps using filters with differing pore sizes.
(E) Specific bacteria are added to the solution, because selected
species allow specific sequences of foreign DNA to be
incorporated into their own.

64. During translation, how is the subsequent amino acid transferred from
the tRNA that brought it into the ribosome to the nascent protein
strand?
(A) The two are brought into close proximity, and the amino acid
spontaneously joins the polypeptide due to hydrophobic
interactions.
(B) The transfer requires the expense of ATP to break one bond and
form the other.
(C) The rRNA of the ribosome serves to catalyze the transfer from the
tRNA to the polypeptide strand.
(D) Two proteins of the large ribosomal subunit facilitate the transfer
from the tRNA to the polypeptide strand.
(E) The interactions of the proteins and rRNA of both ribosomal
subunits physically distort the tRNA—amino acid bond to the
breaking point, allowing its facilitated transfer to the polypeptide.
 CHAPTER 3

The Molecular Biology of Eukaryotes

65. Which of the following is responsible for the synthesis of tRNA?

(A) DNA polymerase I
(B) RNA polymerase II
(C) DNA polymerase III
(D) RNase
(E) RNA polymerase III

66. The type of mobile genetic element that has a great similarity to
certain types of viruses is
(A) an intron
(B) an LTR retrotransposon
(C) a DNA transposon
(D) a LINE
(E) a composite SINE transposon

67. The cumulative length of DNA within a single human nucleus, if laid
end to end, would be about 1.8 meters. Of that, approximately how
much codes for human proteins?
(A) 14 cm
(B) 50 cm
(C) 3.6 cm
(D) 5.4 cm
(E) 61 cm

68. Which of the following best describes a telomere?

 (A) A single stretch of DNA that codes for all nucleic acid
polymerases
(B) A region of intensely staining proteins dispersed throughout
chromosomes associated with active transcription
(C) A dispersed DNA sequence that codes for most cytoskeletal
proteins associated with intracellular communications
(D) A repetitive sequence found on the ends of chromosomes
(E) A protein-based structure found in the cytoplasm associated with
controlling cellular division

69. The replisome is best associated with

(A) transcription of mRNA
(B) translation within the mitochondria
(C) replication within the nucleus
(D) transcription of tRNA and rRNA
(E) transcription of cDNA

70. A back mutation can affect genetic expression by

(A) changing a conditional mutation into a lethal mutation
(B) changing a conditional mutation into a forward mutation
(C) changing the genotype into the phenotype
(D) suppressing the original phenotype
(E) restoring the original genotype

71. Which of the following is NOT a posttranscriptional modification of

hnRNA performed by eukaryotes?
(A) The addition of a 3′ polyA tail
(B) The addition of a 5′ methylguanosine cap
(C) The removal of introns
(D) The addition of an ATP triphosphate cap
(E) The retention of exons

72. The bacterial operon is controlled by a digital mechanism, with

expression of the operon either fully off or fully on. Which of the
 following best describes the eukaryotic version?
(A) Variations in expression levels based on remote activators and
suppressors
(B) A single remote suppressor that shuts off gene expression
regardless of other factors
(C) Cis binding of either a repressor or an activator
(D) Trans binding of a single repressor or activator
(E) A single remote activator that fully derepresses gene expression

73. In what way are the mechanisms controlling gene expression by

protein and steroid hormones similar?
(A) Both bind to specific receptors.
(B) Both produce second messengers that eventually produce DNA
binding proteins.
(C) Both bind to receptors that eventually produce signal production of
RNA polymerase.
(D) Both specifically bind to surface receptors.
(E) Both have structural similarities that allow the cross-reactivity of
receptor binding.

74. The component of the RNA polymerase holoenzyme that determines

the specificity of the precise DNA binding site in eukaryotes is the
(A) σ70 subunit
(B) the TFIID complex + σ factor
(C) RNA polymerase I
(D) the α + βl + β2 chains
(E) the 2α + β + β′ chains

75. Which of the following best describes the function of RNA

polymerase?
(A) It reads a template DNA strand 5′ to 3′ and synthesizes a DNA
strand 3′ to 5′.
(B) It reads a template RNA strand 5′ to 3′ and synthesizes a DNA
strand 3′ to 5′.
 (C) It reads a messenger RNA strand and synthesizes proteins.
(D) It reads a template DNA strand 5′ to 3′ and synthesizes an RNA
strand 5′ to 3′.
(E) It reads a template DNA strand 3′ to 5′ and synthesizes an RNA
strand 5′ to 3′.

76. Which of the following is the best description of a proto-oncogene?

(A) A normal, important growth-regulating gene
(B) A gene that codes for a catabolite activator protein
(C) A specific gene sequence that is observed in lower animals but
which is a pseudogene in humans
(D) Any DNA sequence that contains a TFIIB recognition element
(E) Any gene that produces an oncogenic effect

77. An inversion mutation within spacer DNA would most likely do what
to the resulting phenotype?
(A) It would be lethal.
(B) It would prevent the expression of the nearest downstream gene.
(C) It would have no effect.
(D) It would change a constitutive gene into one that was repressible.
(E) The effects of the mutation would only be observable by radically
changing the growth conditions.

78. The molecular component(s) responsible for preventing supercoiling

during DNA replication is (are)
(A) helicase
(B) topoisomerase
(C) DNA polymerase I
(D) primase
(E) SSBs

79. The environment can regulate genetic expression by

(A) decreasing the length of telomeres
(B) influencing DNA methylation
 (C) relocating the positions of centromeres
(D) denaturing histones
(E) reorganizing centrosomes

80. Certain genotypes of human papillomavirus (HPV) can cause cancer

because
(A) the virus causes cell death by interfering with the p53 protein
(B) the viral E7 oncogene protein binds to protein Rb, thereby
preventing the infected cell from controlling its own growth
(C) viral replication causes disruptions in DNA repair
(D) viral replication interferes with the Wnt control pathway by
causing loss of function
(E) the viral L1 protein disrupts proper chromosome sorting during
mitosis

81. The eukaryotic equivalent of a bacterial repressor is

(A) a neutral assemblage of regulatory proteins in cis to the affected
gene
(B) an inhibitor binding at the operator region
(C) a cofactor in an allosteric location
(D) an inhibiting protein in trans
(E) a sudden influx of either Ca2+ or Na+

82. The proper sequence in chromatin packaging is

(A) nucleosome → heterochromatin → chromatin fiber →
chromosome
(B) nucleosome → chromatin fiber → heterochromatin →
chromosome
(C) chromosome → chromatin fiber → nucleosome →
heterochromatin
(D) heterochromatin → chromosome → nucleosome → chromatin
fiber
(E) chromosome → heterochromatin → nucleosome → chromatin
fiber
83. When producing an antibody, a lymphocyte will transcribe a single
message; however, two different proteins may be translated from that
single mRNA strand. How does this occur?
(A) The message is polycistronic.
(B) The message can be translated in two different directions for
producing two different proteins.
(C) Alternate splicing can account for the different products.
(D) Splicing may retain one or more introns that are then translated
into a separate domain of the final protein.
(E) The message is dicistronic.

84. A chromosomal region rich in simple-sequence repeated DNA

describes which of the following?
(A) Microsatellites and telomeres
(B) Telomeres and centromeres
(C) Histones and nucleosomes
(D) Microsatellites, telomeres, and centromeres
(E) Nucleosomes and centrosomes

85. The eukaryotic equivalent of the bacterial hairpin terminator is

(A) the mRNA leader sequence
(B) the 3′ polyA tail
(C) the 5′ GTP triphosphate cap
(D) the 7-methylguanosine cap
(E) the stop codon in the genetic code

86. A ribozyme is
(A) the enzyme within the ribosome that terminates translation
(B) the enzyme within the spliceosome that rejoins exons
(C) any RNA that is capable of cleaving itself
(D) the enzyme within the spliceosome that rejoins introns
(E) a collection of introns that shuts down transcription of various
genes
87. Which of the following is the best description of a nucleosome?
(A) A cluster of eight identical proteins wrapped around 292
nucleotide pairs
(B) A compact collection of splicing factors and snRNPs
(C) A collection of proteins that aid in the export of ribosomal subunits
out of the nucleus
(D) A cluster of four pairs of proteins supporting 146 nucleotide base
pairs with an attached linker
(E) The region within the nucleus where tRNA and rRNA are
transcribed and ribosomal subunits are assembled

88. Which of the following is one of the best tools for following gene
expression?
(A) Microarray
(B) Western blot
(C) Southern blot
(D) Electrophoresis
(E) Northern blot

89. The Shine-Dalgarno sequence is found

(A) in the promotor region of inducible genes
(B) in the operator region of inducible genes
(C) in the promotor region of repressible genes
(D) in the leader sequence of mRNA
(E) on the edges of introns
 CHAPTER 4

Microbiology

90. Which of the following characteristics least distinguishes a fungus

from a bacterium?
(A) Cell wall composition
(B) Ribosomal structure
(C) The presence of organelles
(D) Membrane composition
(E) Genomic organization

91. Microorganisms vary widely in size. Why is the presence of a cestode

parasite, which can reach lengths measured in meters, typically
diagnosed by microbiologists?
(A) Because the subcellular structures used to differentiate species
must be observed under a microscope.
(B) Because the ova found in the stool samples usually used for
identification are microscopic in size.
(C) Because these organisms inhabit the digestive tract and are best
observed by colonoscopy.
(D) Because these organisms are frequently alone in the digestive tract
and must reproduce asexually like bacteria.
(E) Because of tradition; better serologic diagnostic methods can now
be used more efficiently.

92. Bacteria provide the basis for the food chain associated with
communities of tube worms and crustaceans near deep-sea
hydrothermal vents. How can these bacteria grow in the absence of
light?
(A) They use the heat energy provided by the subterranean vent.
 (B) They feed on the dead organisms common within the community.
(C) They use light energy that comes from the phosphorescent fish
within the community.
(D) They feed on the detritus that constantly rains down from
organisms at higher sea levels.
(E) They use the energy provided by the minerals spewed out from the
vents.

93. To function, all viruses must possess

(A) a glycolipid coat and DNA genome
(B) a genome of RNA, a protein coat, and a phospholipid envelope
(C) a protein coat and a nucleic acid genome
(D) a genome of either DNA or RNA and a phospholipid envelope
(E) a protein coat filled with a nucleic acid genome and a transcription
enzyme

94. Which of the following structures targeted by an antibiotic would

generally be the least preferable for use in humans?
(A) The bacterial cell wall
(B) The bacterial ribosome
(C) A protein involved in bacterial replication or transcription
(D) The bacterial cell membrane
(E) Specific bacterial metabolic enzymes

95. Which of the following least distinguishes the bacterial from the
eukaryotic ribosome?
(A) Function
(B) Molecular weight
(C) Sedimentation coefficient
(D) Nucleic acid content
(E) Protein composition

96. Which structure is most like the bacterial genome?

(A) The Golgi apparatus
 (B) A eukaryotic chromosome
(C) A viral genome
(D) A kinetoplast of some protozoans
(E) A mitochondrial genome

97. What is the truest relationship between a polyhedral virus and a

bacterial coccus?
(A) Their genomes are similar in structure and only differ in size.
(B) The only similarity is their roughly spherical general shape.
(C) The cell wall of the bacterium is analogous in function to that of
the coat of the virus.
(D) The cell membrane of the bacterium is analogous in function to
that of the envelope of the virus.
(E) Both survive only by acting as parasites on host cells.

98. The _____________ of the bacterial flagella are embedded in the

______________ of the bacterium.
(A) basal bodies; cell wall
(B) hooks; cell membrane
(C) axial filaments; outer glycocalyx
(D) basal bodies; cell membrane
(E) hooks; cytosol

99. What chitin is to a fungus, ______________ is to a bacterium.

(A) cellulose
(B) actin
(C) peptidoglycan
(D) lactose
(E) chromatin

100. Some bacteria can form endospores. Which of the following is the best
description of these structures?
(A) They are an asexual form of reproduction analogous to the spores
of fungi.
 (B) They are the only means of sexual reproduction found in bacteria.
(C) They are a survival mechanism for bacteria formed when resources
become limited or conditions hostile.
(D) They are formed after conjugation as observed with some enteric
bacteria.
(E) They are a fully functioning and metabolizing reduction of the
original bacterium adapted to the harsher conditions that triggered
their formation.

101. Eukaryotic cells divide by mitosis. Bacteria divide by

(A) lateral schism
(B) binary fission
(C) meiosis
(D) mitosis, wherein both daughter cells get one half of the original
contents of the mother cell
(E) fragmentation

102. Double-stranded DNA viruses include

(A) Ebola virus and Lassa virus
(B) bacteriophage T4 and variola
(C) rhinovirus and poliovirus
(D) rotavirus and reovirus
(E) parvovirus and phage f X174

103. Both viruses and rickettsia

(A) metabolize resources from their host cell
(B) undergo schizogony to create forms that are infectious
(C) spread host to host by sexual contact
(D) are obligate intracellular parasites
(E) can be observed inside the host cell by light microscopy

104. Fungi are dimorphic. This means they can

(A) exist in two forms—infectious and noninfectious
(B) exist in two forms—haploid and diploid
 (C) exist in two forms—with or without a cell wall
(D) reproduce both sexually and asexually
(E) exist in two forms—yeasts and filaments

105. Which of the following mutations restores a bacterial phenotype

similar to the wild type but without restoring the original genotype?
(A) Reversion mutation
(B) Back mutation
(C) Suppressor mutation
(D) Frameshift mutation
(E) Conditional mutation

106. If a person is taking a prescription of isoniazid (INH), then you can be

fairly sure he or she is being treated for a possible infection with
(A) Mycobacterium sp
(B) Streptococcus sp
(C) herpesvirus
(D) human immunodeficiency virus
(E) Chlamydia sp

107. The term “pBR322” refers to a tool used in the genetic engineering of
bacteria and is classified as a
(A) plasmid
(B) restriction endonuclease
(C) transposon
(D) restriction fragment
(E) bacteriophage

108. Replica plating refers to a technique used

(A) for ensuring accuracy by running duplicates during the
phenotyping of new cultures
(B) for the identification of proper host-phage combinations
(C) for standard water analysis
(D) for the detection of nutritionally deficient organisms
 (E) for the identification of mobile genetic elements with microarrays

109. Some bacterial plasmids convey an extra degradative or nitrogen-

fixing pathway to a host cell. This type of plasmid is identified as a
(A) fertility plasmid
(B) col plasmid
(C) metabolic
(D) virulence
(E) Hfr plasmid

110. Which of the following best describes cDNA?

(A) It is produced directly by removing the introns from hnRNA.
(B) It is produced by back-sequencing from the expressed protein.
(C) It is produced directly by removing the exons from hnRNA.
(D) It is produced from DNA by using a restriction endonuclease.
(E) It is produced from mRNA by using reverse transcriptase.

111. Autoradiographs can be used to

(A) identify the location of specific RNA sequences on a Southern blot
(B) identify the location of specific proteins on a Western blot
(C) locate gene loci on individual chromosomes
(D) split DNA and produce sticky ends
(E) update gene libraries

112. What do viroids and multipartite viruses have in common?

(A) They are all negative sense viruses.
(B) They are all enveloped.
(C) Their host cells are prokaryotic.
(D) They are all associated with plants.
(E) They are all helical in morphology.

113. The microorganism that is best known for its mechanism of motility
called cytoplasmic streaming is
 (A) a cellular slime mold
(B) Plasmodium sp
(C) an acellular slime mold
(D) Entamoeba histolytica
(E) a mycoplasma

114. Which of the following human parasites requires a crawfish for part of
its life cycle?
(A) Taenia saginata
(B) Balantidium coli
(C) Klebsiella pneumoniae
(D) Enterobius vermicularis
(E) Paragonimus westermani

115. The presence of which gas would be toxic for a facultative anaerobe?
(A) Water vapor
(B) Oxygen
(C) Carbon dioxide
(D) Nitrogen
(E) Chlorine

116. Genital warts are caused by a

(A) virus
(B) bacterium
(C) fungus
(D) protozoan
(E) microscopic nematode

117. If you discovered a mutant bacterium that could use DNA as a sole
carbon source, you would
(A) panic, because it would probably be 100 percent lethal to humans
(B) become greatly concerned, because it would probably be
pathogenic in humans
(C) be unconcerned, because most bacteria have this ability
 (D) become somewhat concerned, because it would likely reach
equilibrium with the human population
(E) be unconcerned, because this ability would eventually cause it to
consume its own DNA

118. Which of the following statements is true concerning transformation?

(A) It is the process that enables mitochondria to remain functional in
eukaryotic cells.
(B) A virus stripped of its capsid could still produce a successful
infection of a host cell through this process.
(C) It is the only mechanism that provides genetic mixing in bacteria.
(D) Seven genera of bacteria use this process to produce endospores.
(E) Trichinella worms use this process to convert adjacent host cells
into nurse cells to support their survival.

119. A fungus classified as an ascomycete would produce

(A) asexual spores within a large sac
(B) large, thick-walled sexual spores
(C) asexual spores born on stalks
(D) sexual spores within small sacs
(E) spores within a structure we would identify as a mushroom

120. You have a vital unit of human plasma that you are concerned is
contaminated with Candida albicans. What would be the best way to
sterilize the plasma while retaining its medicinal value?
(A) Expose the entire bag to ultraviolet light
(B) Boil the unit for 30 minutes
(C) Filter the unit through a 0.45-μm filter
(D) Add 2 percent gluteraldehyde to the unit
(E) Add 10 percent ethanol to the unit

121. If the generation time of E. coli is 20 minutes and you started with 10
cells in a growing culture, how many cells would you have at the end
of three hours?
 (A) 5,120
(B) 20
(C) 1,280
(D) 12,240
(E) 10,240

122. Ringworm is caused by a

(A) bacterium
(B) fungus
(C) virus
(D) microscopic nematode
(E) protozoan

123. Bacterial cultures progress through four phases of growth when

retained within a closed system. At which phase would you expect the
greatest ratio of dead to living cells?
(A) During the lag phase
(B) During both the lag phase and the log phase (It would be
impossible to distinguish between the two.)
(C) During the stationary phase
(D) During the logarithmic decline phase
(E) During the log phase

124. The staining technique used in a microbiology lab to differentiate the

two major types of bacterial cell walls is the
(A) negative stain
(B) endospore stain
(C) acid-fast stain
(D) simple stain
(E) Gram stain

125. Bacteria and fungi are alike in that

(A) they can both exist in unicellular form
(B) their cell walls are composed of the same material
 (C) their genomes are organized in the same fashion
(D) their ribosomes are of identical construction
(E) they are both capable of both sexual and asexual reproduction

126. The proper sequence for the replication of a virus within a host cell is
(A) attachment → uncoating → biosyntheis → penetration →
maturation → release
(B) penetration → uncoating → maturation → biosynthesis →
attachment → release
(C) attachment → penetration → uncoating → biosynthesis →
maturation → release
(D) uncoating → maturation → biosynthesis → release → attachment
→ penetration
(E) release → penetration → uncoating → attachment → biosynthesis
→ maturation

127. If you put hydrogen peroxide on a colony of bacteria and bubbles were
given off, what would you likely conclude about the organism?
(A) It is probably autotrophic.
(B) It is probably aerobic.
(C) Its natural habitat is aquatic.
(D) It is probably an obligate anaerobe.
(E) It has a glycocalyx that reacts with the water.

128. If you suspected someone was showing signs of inhalation anthrax,

what would you do?
(A) Rush the person into isolation to prevent the patient from
spreading the bacterium by coughing.
(B) Rinse the patient’s lungs with a disinfectant.
(C) Require immediate bed rest to allow the patient’s immune system
to fight off the infection.
(D) Administer antibiotics immediately.
(E) Administer a whole blood transfusion to provide antibodies to fight
off the infection.
129. A viral genome that can be translated by reading the template strand in
both the 5′ to 3′ and the 3′ to 5′ directions indicates that
(A) it is a virus with an ambisense genome
(B) it is a virus with a positive-sense genome
(C) it is any virus that requires reverse transcriptase for replication
(D) it is a virus with a negative-sense genome
(E) none of the above

130. If you isolated an organism that lacked a cell wall but had only 70S
ribosomes and a circular, double-stranded genome, then you would
have
(A) a protozoan
(B) a primitive animal
(C) a eubacterium
(D) a mutant fungus
(E) a slime mold

131. Of the following, which is NOT descriptive of all viruses?

(A) They are all crystallizable.
(B) They all have a lipid bilayer cell membrane.
(C) They are all incapable of metabolism.
(D) They all demonstrate an eclipse period during replication.
(E) They do not grow or differentiate.

132. If you discovered an infectious agent that lacked both RNA and DNA,
what would you suspect?
(A) A laboratory error in analysis
(B) A mutant virus
(C) An organism with a new, previously unidentified form of genomic
material
(D) An endospore so old that its genome had degraded
(E) A prion

133. Bacterial genetic engineers use generalized transduction by

 (A) allowing a lysogenic bacteriophage to package specific DNA
sequences to carry to another cell
(B) allowing naked DNA to be taken up randomly by susceptible
bacteria
(C) using a gene gun to insert specific sequences into a cell
(D) using restriction endonucleases to break apart desired sequences so
they can pass into the target cell for reassembly within the new
host cytoplasm
(E) allowing a lysogenic bacteriophage to package random DNA
sequences to carry to another cell

134. Which of the following best describes how halogens provide

disinfection?
(A) By upsetting the osmotic balance between the interior and exterior
of the cell
(B) By denaturing most organic materials
(C) By disrupting cell-wall synthesis
(D) By increasing the rate of efflux of substances from the cell
(E) By decreasing the pH of the interior of the cell to very acidic
conditions

135. An infectious agent presenting with a complex protein structure, often

incorporating baseplates or tail fibers, best describes
(A) a T-even bacteriophage
(B) a prion
(C) a toxogenic bacterium
(D) a bacterium possessing both flagella and pili
(E) an organism that uses schizogony and a reproduction strategy

136. Bacteria can frequently acquire antibiotic resistance by horizontal

transfer. The most common mechanism of this acquisition is through
(A) transformation by plasmids
(B) generalized transduction by lysogenic bacteriophages
(C) bacterial conjugation
(D) a classical exchange of equal-sized genome copies
(E) endocytosis
 CHAPTER 5

The Eukaryotic Cell

137. Classes of lipids in an animal cell membrane include which of the

following?
(A) Glycolipids and cholesterol
(B) Cholesterol and phospholipids
(C) Peptidoglycans, cholesterol, and glycolipids
(D) Phospholipids, cholesterol, and glycolipids
(E) Cholesterol, phospholipids, and peptidoglycans

138. Which of the following is the best explanation for the relationship
between the number of chromosomes and the organism in which they
are found?
(A) The greater the number of chromosomes, the greater the number of
genes.
(B) The greater the number of chromosomes, the more complex the
resulting organism but the fewer genes present in the DNA.
(C) The greater the number of chromosomes, the longer-lived the
resulting organism.
(D) There is no consistent relationship between the number of
chromosomes and the number of genes or the resulting complexity
of the organism.
(E) The greater the number of chromosomes, the greater the number of
genes but the shorter-lived the organism.

139. Water passes through any cell membrane by

(A) simple diffusion
(B) channel-mediated passive transport
 (C) simple diffusion in a terrestrial organism but channel-mediated
passive transport in an aquatic one
(D) carrier-mediated active transport
(E) carrier-mediated in a terrestrial organism but simple diffusion in an
aquatic one

140. Membrane-associated β barrels are classified as _______________

proteins.
(A) lipid-linked
(B) transmembrane
(C) protein-attached
(D) hydrophobic
(E) anchor

141. Which of the following CANNOT be used to observe the cellular

cytoskeleton?
(A) Fluorescence microscopy
(B) Laser confocal microscopy
(C) X-ray crystallography
(D) Transmission electron microscopy
(E) Phase contrast microscopy

142. The most concise explanation of the cell cycle through mitosis is
indicated by
(A) 4n → 2n → 1n
(B) 1n → 2n → 4n → 2n
(C) 2n → 4n → 2n
(D) 2n → 4n → 2n → 1n
(E) 4n → 2n

143. Of the following, which indicates protein movement by vesicular

transport?
(A) Moving from the cytosol to the nucleus
(B) Moving from the cytosol to mitochondria
 (C) Moving from the endoplasmic reticulum to the Golgi apparatus
(D) Moving from the nucleus to the cytosol
(E) Moving from the cytosol to peroxisomes

144. The flow of ions across a membrane is best associated with

(A) β barrels
(B) peripheral membrane proteins
(C) glycosylated proteins
(D) active transport
(E) α-helices

145. Which of the following is the truest statement concerning

cytoskeletons?
(A) Cytoskeletons are found in eukaryotes with cell walls.
(B) Cytoskeletons are found only in eukaryotes.
(C) Cytoskeletons are found in plant cells.
(D) Cytoskeletons are found in multicellular organisms.
(E) Cytoskeletons are found in eukaryotic as well as some prokaryotic
cells.

146. Which of the following changes to a membrane would increase its

fluidity?
(A) Increase the percentage of shorter-chained phospholipids
(B) Decrease the percentage of unsaturated fatty acids
(C) Decrease the percentage of shorter-chained phospholipids
(D) Change the disaccharides to trisaccharides
(E) Increase the degree of phosphorylation of the lipids

147. Cellular aneuploidy can be caused by which of the following?

(A) Nondisjunction and trisomy
(B) Translocation, nondisjunction, and trisomy
(C) Trisomy and arrested cell cycle
(D) Cytokinesis
(E) Meiosis
148. Motions expressed by phospholipids in a bilayer include all of the
following EXCEPT
(A) lateral diffusion
(B) rotation
(C) flexion
(D) flip-flop
(E) inversion

149. Gated transport involves the movement of a substance through pores in

a membrane with specific protein accompaniment. Which of the
following identifies a well-known gated transport of a protein?
(A) Movement from the cytosol into the nucleus
(B) Movement from the cytosol into mitochondria
(C) Movement from the endoplasmic reticulum to the Golgi apparatus
(D) Movement from the environment into the cytosol
(E) Movement from the Golgi apparatus to secretory vesicles

150. Which of the following best describes the protein subunits that
comprise a microtubule?
(A) A dimer of intertwined, intermediate filament polypeptides
(B) Overlapping layers of actin and myosin
(C) G-actin monomers arranged into F-actin polymers
(D) α and β tubulin dimers
(E) Two heavy chains linked to two light chains by multiple disulfide
bridges

151. Against a gradient, glucose can cross a membrane by

(A) simple diffusion
(B) channel-mediated passive transport
(C) carrier-mediated passive transport
(D) carrier-mediated active transport
(E) coupled antiport
152. The length of the hydrophobic tails of the membrane’s phospholipids
ensure the proper chemical characteristics vital to living cells. These
are most commonly within what range of carbon atom length?
(A) 8 to 13
(B) 18 to 20
(C) 15 to 21
(D) 19 to 25
(E) 26 to 30

153. Protein import into a chloroplast proceeds in which of the following

sequences?
(A) A signal sequence binds to a receptor; the protein-receptor
complex moves laterally; the protein refolds; and the signal
sequence is removed.
(B) A signal sequence binds to a receptor; the protein refolds; the
protein-receptor complex moves laterally; and the signal sequence
is removed.
(C) A signal sequence binds to a receptor; the signal sequence is
removed; the protein-receptor complex moves laterally; and the
protein refolds.
(D) The signal sequence binds to a receptor; the protein-receptor
complex moves laterally; the signal sequence is removed; and the
protein refolds.
(E) The protein refolds; the signal sequence is removed; the protein
binds to a receptor; and the protein-receptor complex moves
laterally.

154. Ribosomal proteins are synthesized in the _______________ for

transport to the _______________ for subunit assembly.
(A) rough endoplasmic reticulum; cytosol
(B) cytosol; Golgi apparatus
(C) cytosol; nucleus
(D) early endosomes; late endosomes
(E) rough endoplasmic reticulum; smooth endoplasmic reticulum
155. Calcium ions in body fluids are normally _______________ than in
cells.
(A) 200 times lower
(B) 400 times higher
(C) 5,000 times lower
(D) 10,000 times higher
(E) 250,000 times higher

156. Which cytoskeletal components are responsible for chromatid

migration during anaphase?
(A) Intermediate filaments and microfilaments
(B) Microtubules
(C) Overlapping actin and myosin fibers
(D) Microfilaments
(E) Intermediate filaments

157. Enzymes for DNA synthesis are manufactured during which stage of
the cell cycle?
(A) S phase
(B) Telophase
(C) G2 phase
(D) M phase
(E) G1 phase

158. Glycosylated proteins embedded within the cell membrane

(A) decrease membrane permeability
(B) serve as anchors for the cytoskeletal framework
(C) are most frequently associated with cell signaling
(D) almost never have disulfide cross-linking
(E) are only synthesized during mitosis

159. Chaperones are best associated with

(A) vesicular transport
 (B) protein folding within the lumen of the endoplasmic reticulum
(C) protein folding within the cytosol
(D) nuclear transport
(E) the signal peptidase removal of signal sequences

160. Which of the following does NOT describe what cytoskeletal

microfilaments are responsible for in the eukaryotic cell?
(A) Amoeboid movement and cytoplasmic streaming
(B) Formation of the cleavage furrow following cytokinesis
(C) Maintenance of the cell shape
(D) Acting as contractile fibers in muscle cells
(E) Formation of the interior structure of flagella and cilia

161. What line of evidence does NOT support the endosymbiotic theory of
the origin of mitochondria?
(A) Mitochondria have their own genome that resembles that of a
bacterium.
(B) Mitochondria carry out their own transcription and translation.
(C) Mitochondria have a genetic code different than that of most of the
cells in which they are found.
(D) Mitochondrial membranes are surrounded by an unusual second
membrane.
(E) Mitochondria have different forms for RNA than eukaryotic cells
do.

162. The phases of mitosis proceed in the following sequence:

(A) prophase → prometaphase → metaphase → anaphase → telophase
(B) metaphase → prometaphase → anaphase → telophase → prophase
(C) prophase → anaphase → metaphase → prometaphase → telophase
(D) telophase → anaphase → prophase → prometaphase → metaphase
(E) anaphase → telophase → metaphase → prophase → prometaphase

163. Which of the following is the proper sequence of events for a cell
undergoing apoptosis?
 (A) Nuclear fragmentation → chromosome condensation → bleb
formation → DNA digestion → cytoplasmic fragmentation
(B) Chromosome condensation → nuclear fragmentation → DNA
digestion → cytoplasmic fragmentation → bleb formation
(C) DNA digestion → chromosome condensation → nuclear
fragmentation → cytoplasmic fragmentation → bleb formation
(D) Cytoplasmic fragmentation → nuclear fragmentation → bleb
formation → chromosome condensation → DNA digestion
(E) Bleb formation → cytoplasmic fragmentation → DNA digestion
→ nuclear fragmentation → chromosome condensation

164. Which of the following does NOT correctly describe the structure or
function of the eukaryotic nucleus?
(A) The inner membrane is lined with a nuclear lamina that binds to
chromosomes.
(B) The outer membrane is continuous with the endoplasmic
reticulum.
(C) Materials enter and exit the nucleus through pores composed of a
single nuclear barrel body protein.
(D) Gated transport of a protein into the nucleus requires that it
possess a specific amino acid sequence localization signal.
(E) Proteins passing into or out of the nucleus remain in their folded
configuration.

165. What prevents glucose from being transported out of an epithelial cell
and into the intestinal lumen?
(A) The glucose gradient is contrary to this direction of flow.
(B) The glucose is imported with the sodium-potassium pump.
(C) The glucose is imported with sodium antiport.
(D) The glucose is imported with sodium symport.
(E) Too much ATP expense would be required for the cell to drive this
function.

166. What is the primary function of the mitochondria within a cell?

(A) They generate the bulk of the ATP required for cellular functions.
 (B) They regulate all respiration processes.
(C) They provide all the tRNA used by the cell in translation.
(D) They break down and detoxify damaging materials generated
within the cell.
(E) They are the site where glycolysis takes place.

167. If you were observing mitosis during metaphase, which of the

following would be the correct sequence of structures if you were
scanning from one pole of the cell to the opposite pole?
(A) Centriole → spindle microtubules → kinetochore → centromere
→ kinetochore → spindle microtubules → centriole
(B) Centriole → spindle microtubules → kinetochore → centrosome
→ kinetochore → spindle microtubules → centriole
(C) Spindle microtubules → kinetochore → centriole → centromere
→ centriole kinetochore → spindle microtubules
(D) Centromere → kinetochore → spindle microtubules → telomere
→ spindle microtubules → kinetochore → centromere
(E) Telomere → centriole → spindle microtubules → centromere →
kinetochore → centromere → spindle microtubules → centriole →
telomere

168. Six traits are common to all forms of cancer. Which of the following is
NOT one of those common traits?
(A) Evasion of apoptosis
(B) Autoproduction of growth signals
(C) Mutagenesis by chemicals or radiation
(D) Self-sustained angiogenesis
(E) Insensitivity to tumor suppression

169. Some cellular organelles are present in numbers that sometimes exceed
a thousand per cell. Which of the following fits that description?
(A) Chloroplast
(B) Peroxisome
(C) Endosome
 (D) Mitochondrion
(E) Golgi apparatus

170. Which of the following statements is correct concerning the

relationship between the rough endoplasmic reticulum (RER) and the
smooth endoplasmic reticulum (SER)?
(A) Protein synthesis occurs within the RER, while protein
glycosylation occurs in the SER.
(B) Ribosomes are concentrated near the RER but are lacking in the
SER.
(C) Proteins are moved from the RER to the SER by vesicular
transport.
(D) Membrane-bound proteins are synthesized in the cytosol and
become embedded in the membrane in the RER, while proteins for
secretion are manufactured within the lumen of the SER.
(E) Protein synthesis occurs within both RER and SER segments, but
signal sequences determine into which area they go.

171. Which of the following is the best description of the function of the
nucleolus?
(A) It is the primary site of active mRNA production.
(B) It is strongly associated with ribosomal construction.
(C) It is the source of nuclear ATP production.
(D) It is the area of the nucleus with the greatest concentration of
RNAi.
(E) It is the area where DNA synthesis occurs.

172. What cellular organelle is associated with the destruction of

phagocytosed materials?
(A) The nucleus
(B) The peroxisome
(C) The Golgi apparatus
(D) The rough endoplasmic reticulum
(E) The lysosome
173. Apoptosis is a complex mechanism. Which is NOT involved in this
process?
(A) Cytochrome c
(B) A death receptor
(C) Caspase
(D) Apoptosome
(E) Peroxisome

174. Which of the following is the best analogous description of the

function of the nucleus?
(A) A library
(B) A highway system
(C) A town council
(D) A police department
(E) Power utilities

175. Interference in cell-to-cell signaling can be caused by

(A) defective gated transport
(B) a defective sodium-potassium pump
(C) antibodies binding to surface proteins
(D) a defect in a gene that codes for part of the cytoskeleton
(E) increased cholesterol content in the cell membrane

176. Which of the following is incapable of movement across a membrane

without assistance?
(A) Water
(B) Benzene
(C) Sodium ions
(D) Urea
(E) Oxygen

177. Membrane proteins have a wide variety of functions EXCEPT

(A) transporting substances
 (B) storing materials
(C) anchoring structures
(D) serving as receptors
(E) having enzymatic activity

178. All of the following are associated with active transport EXCEPT
(A) symport
(B) ATP-driven pumps
(C) antiport
(D) light-driven pumps
(E) transport of water

179. Characteristics of the structure of a transmembrane α-helix include

(A) having a length of about 10 amino acids
(B) being rich in hydrophilic amino acids
(C) generally being surrounded by cholesterol molecules
(D) having hydrophobic side chains on the outside of the molecule
(E) always being in dimeric form

180. Cytoskeletal proteins and structures are associated with all of the
following EXCEPT
(A) movement of vesicles through the cell
(B) cilia structure
(C) cytokinesis
(D) importation of LDL through a membrane
(E) attachment to anchor proteins

181. Which of the following is NOT associated with cell-to-cell adhesions?

(A) Collagen
(B) Desmosome
(C) Gap junction
(D) Tight junction
(E) Hemidesmosome
 CHAPTER 6

Specialized Cells and Tissues

182. Schwann cells are a major component of

(A) the nervous system
(B) the digestive system
(C) the excretory system
(D) the immune system
(E) the musculoskeletal system

183. The sliding filament model is best associated with

(A) bone marrow
(B) connective tissue
(C) cartilage
(D) muscles
(E) skin

184. All of the following are related to a muscle cell EXCEPT

(A) sarcomere
(B) I band
(C) T zone
(D) Z disk
(E) troponin

185. The primary neurotransmitter involved at the neuromuscular synapse

is
(A) dopamine
(B) histamine
(C) D-serine
 (D) acetylcholine
(E) serotonin

186. The action potential of a nerve cell is maintained by the vigorous

activity of
(A) contractile vesicles
(B) sodium-potassium pumps
(C) actin-myosin interaction
(D) nodes of Ranvier
(E) Ca2+ influx

187. The nucleus of a neuron resides in the

(A) axon
(B) myelin sheath
(C) cell body
(D) dendrites
(E) node of Ranvier

188. Which of the following cell types has the greatest number of
mitochondria?
(A) Osteocyte
(B) Adipocyte
(C) Erythrocyte
(D) Fibroblast
(E) Muscle cell

189. A nerve is
(A) a cell of the central nervous system
(B) a bundle of axons
(C) a cluster of neurons and nurse cells
(D) composed of an axon and numerous dendrites
(E) totally surrounded by a myelin sheath

190. Muscle cells are covered with a membrane sheath called

 (A) the sarcoplasm
(B) the sarcolemma
(C) the muscle fiber
(D) striations
(E) the myofibril

191. Bone structure is maintained by the interaction of two cell types,

which involves
(A) osteoclasts degrading bone material while osteoblasts deposit bone
material
(B) osteocytes in stasis with osteoblasts in motion
(C) chondrocytes degrading bone material while osteocytes deposit
bone material
(D) chondrocytes depositing bone material while osteocytes degrade
bone material
(E) osteoclasts in stasis with chondrocytes in motion

192. Which of the following is NOT true about the sodium-potassium

pump?
(A) The sodium level is normally higher outside the cell.
(B) Three sodium atoms are exported for every two potassium atoms
imported.
(C) The expense of ATP is required for the pump to operate.
(D) The pump is antiport.
(E) The potassium level is normally higher outside the cell.

193. The sarcoplasmic reticulum of the muscle cell is most closely related
to _______________ in other cells.
(A) the Golgi apparatus
(B) a large collection of endosomes
(C) the smooth endoplasmic reticulum
(D) mitochondria
(E) the rough endoplasmic reticulum
194. What is the function of an axon?
(A) It provides genetic control by being interspersed between introns.
(B) It provides a physical barrier between the brain and the peripheral
nervous system.
(C) It separates one neuron from another.
(D) It conducts action potentials from the neuron body to the synapses.
(E) It establishes the threshold for producing an action potential.

195. Keratinized squamous epithelium describes cells

(A) that line the lumen of the small intestine
(B) that line the interior of the stomach
(C) that cover a nerve bundle
(D) that comprise tendons
(E) that make up the upper layers of the skin

196. The function of the nodes of Ranvier is to

(A) increase the rate of conduction down the axon
(B) increase the respiration rate for higher ATP production
(C) decrease the likelihood of “cross talk” between neurons
(D) increase the connectivity between neurons
(E) decrease the stimulation required to initiate an action potential

197. What differentiates a cardiac muscle cell from a skeletal muscle cell?
(A) A cardiac muscle cell is branched, whereas a skeletal muscle cell
is unbranched.
(B) A cardiac muscle cell contracts slowly, whereas a skeletal muscle
cell contracts rapidly.
(C) Cardiac muscle cells are nonstriated, whereas skeletal muscle cells
are striated.
(D) A cardiac muscle cell is unbranched, whereas a skeletal muscle
cell is branched.
(E) The nucleus of a cardiac muscle cell is within the sarcoplasm,
whereas the nucleus of a skeletal muscle cell lies on the periphery
of the cell.
198. What cell type in humans is incapable of transcription?
(A) Neuron
(B) Erythrocyte
(C) Fibroblast
(D) Osteocyte
(E) Chondrocyte

199. During the transmission of an action potential down a neuron, what

occurs in the depolarization phase?
(A) Sodium expulsion from the cell drops the polarity to −70 mV.
(B) The potassium channels open, and K+ diffuses out of the cell.
(C) The sodium-potassium pumps raise the polarity to +30 mV.
(D) Sodium rapidly enters the cell, raising the polarity to +30 mV.
(E) The sodium-potassium pumps cease working for about 10
milliseconds, then the voltage stabilizes.

200. What two types of human cells are known to have arrested cell cycles?
(A) Memory cells and neurons
(B) Lymphocytes and osteocytes
(C) Bone marrow stem cells and neurons
(D) Erythrocytes and epithelial cells
(E) α and β cells of the pancreas

201. What neurotransmitter combination is found only in the brain?

(A) Acetylcholine and endorphins
(B) Endorphins and norepinephrine
(C) Seratonin and GABA
(D) Acetylcholine and norepinephrine
(E) GABA and acetylcholine

202. Thin filaments of the muscle cell are composed of all of the following
EXCEPT
(A) actin
 (B) troponin
(C) tropomyosin
(D) myosin binding sites
(E) myosin

203. An action potential is propagated down a neuron by

(A) ligand-gated ion channels
(B) mechanically gated ion channels
(C) voltage-gated ion channels
(D) stress-activated ion channels
(E) unregulated ion channels

204. Nerve agents such as VX and sarin impair signal transduction through
the neuromuscular synapse by
(A) preventing the release of acetylcholine, which prevents muscle
contraction
(B) chelating Ca2+ ions, which prevents muscle contraction
(C) preventing the reuptake of degraded acetylcholine components by
the neuron, which greatly weakens muscle contraction
(D) binding to cholinesterase, which prevents the recycling of the
neurotransmitter and greatly weakens muscle contraction
(E) blocking the acetylcholine receptors on the muscle cells, which
prevents muscle contraction

205. What cells produce the white in the white matter of the CNS?
(A) Schwann cells
(B) Oligodendrocytes
(C) M cells
(D) Macrophages
(E) Dendritic cells

206. What differentiates a stimulatory (or excitatory) neuron from an

inhibitory neuron?
 (A) A stimulatory neuron activates Na+ channels on the postsynaptic
cell, whereas an inhibitory neuron opens Cl− channels.
(B) Stimulatory neurons connect to adjacent neurons along the axon,
whereas inhibitory neurons connect to the cell body.
(C) A stimulatory neuron opens Ca2+ channels on the postsynaptic
cell, whereas an inhibitory neuron opens Na+ channels.
(D) An inhibitory neuron releases dopamine, whereas a stimulatory
neuron releases GABA.
(E) A stimulatory neuron passes its action potential through axon
bulbs, whereas an inhibitory one conveys its potential via its
dendrites.

207. It is observed that a cell in culture does not respond with a second
messenger signal following exposure to a hormone. Which of the
following is true about this situation?
(A) The cell would respond if the hormone level were increased
tenfold.
(B) The cell might still respond to a different hormone.
(C) The cell was flooded with too high a level of hormone, which
overloaded its ability to respond.
(D) The defect must be within the cellular kinases.
(E) The problem is most likely a defective hormone.

208. Which of the following cells have the highest level of peroxisomes?
(A) Osteocytes
(B) Lymphocytes
(C) Erythrocytes
(D) Neurons
(E) Hepatocytes

209. When a person is given drugs that interfere with DNA replication,
which of the following cells are most affected?
(A) Neurons
(B) Muscle cells
 (C) Skin cells
(D) Erythrocytes
(E) Glial cells

210. What is the effect of fever on the growth rate of fibroblasts?

(A) Moderately increased body temperature increases the replication
rate.
(B) Greatly increased temperature has no effect on the fibroblast
growth rate.
(C) Moderately decreased body temperature has no effect on the
fibroblast growth rate.
(D) The fibroblast growth rate is unaffected by moderate variations
above or below normal temperature.
(E) Moderately decreased body temperature increases the replication
rate.

211. If half of the calcium present in a muscle cell leaked out of the cell into
the surrounding tissue, what would occur?
(A) Muscle strength would increase.
(B) Signal strength from the neuron to the muscle would increase.
(C) The action potential within the adjacent neuron would be
dampened.
(D) The force of contraction of the muscle cell would decrease.
(E) The muscle cell would contract with its normal strength.

212. Which of the following cells have the least ability to repair damage in
the surrounding tissue?
(A) Hepatocytes
(B) Osteoplasts
(C) Fibroblasts
(D) Muscle cells
(E) Chondrocytes

213. Which of the following is NOT considered a connective tissue?

 (A) Collagenous tissue
(B) Cartilage
(C) Adipose tissue
(D) Blood
(E) Muscle

214. Fetal connective tissue is derived from

(A) the ectoderm layer
(B) placental cells
(C) the mesoderm layer
(D) glial cells
(E) the endoderm layer

215. Which of the following is NOT a proper epithelial categorization?

(A) Stratified squamous
(B) Simple columnar
(C) Stratified cuboidal
(D) Complex columnar
(E) Exocrine gland

216. Reticular connective tissue is best associated with

(A) the endothelial lining of blood vessels
(B) the structural framework of soft organs
(C) tendons
(D) bone tissue
(E) the matrix supporting adipocytes

217. A material NOT associated with the contents of connective tissue is

(A) elastic fiber
(B) tendon
(C) collagen fiber
(D) reticular fiber
(E) ground substance
218. Certain cell types are found only in specific tissues, whereas others are
scattered throughout the body. In which of the following is a goblet
cell NOT found?
(A) The trachea
(B) The eyes
(C) The kidneys
(D) The intestine
(E) The bronchioles

219. Certain cell types are found only in specific tissues. In which of the
following tissues is an M cell found?
(A) Intestinal tissue
(B) Bone tissue
(C) Cartilagenous tissue
(D) Nervous tissue
(E) Muscle tissue

220. Certain cell types are found only in specific tissues. In which of the
following tissues is a glial cell found?
(A) Muscle tissue
(B) Endocrine tissue
(C) Lung tissue
(D) Nervous tissue
(E) Otic tissue

221. Adipose tissue is best associated with the storage of

(A) carbohydrates
(B) lipopolysaccharides
(C) phospholipids
(D) proteins
(E) lipids

222. Bone tissue is best associated with the storage of

 (A) calcium
(B) water
(C) sodium
(D) proteins
(E) potassium

223. Which of the following is associated with both the nervous system and
the endocrine system?
(A) The vagus nerve
(B) Peyer patches
(C) The vena cava
(D) The hypothalamus
(E) Dura mater

224. The concentration of spot desmosomes, tight junctions, and gap

junctions is highest in which of the following?
(A) Skin
(B) Blood
(C) Fibroblasts
(D) Neurons
(E) Alveoli
 CHAPTER 7

The Nervous and Endocrine Systems

225. The nerves contained within the vertebrae are categorized as part of
(A) the parasympathetic nervous system
(B) the central nervous system
(C) the peripheral nervous system
(D) the sympathetic nervous system
(E) the sensory nervous system

226. What are the three primary functions of the myelin sheath?
(A) It protects the neuron from infection; it provides some insulation
properties for the neuron; and it assists in neuron regeneration.
(B) It provides some insulation properties for the neuron; it increases
the speed of signal propagation; and it assists in the formation of
synapses.
(C) It assists in neuron repair; it provides insulation for the axon; and it
increases the speed of signal propagation.
(D) It reduces the neuron’s sensitivity to stimulation; it protects the
neuron from infection; and it assists in neuron regeneration.
(E) It increases the neuron’s sensitivity to stimulation; it assists in the
formation of synapses; and it increases the speed of signal
propagation.

227. The bulk of the ion channels responsible for action potential
propagation are
(A) located along the axon at the nodes of Ranvier
(B) present at the axon bulbs
(C) present within the synapses
(D) located along the axon between the nodes of Ranvier
 (E) at the tips of the dendrites

228. The parathyroid glands are responsible for

(A) providing hormones that increase the inflammatory response
(B) producing epinephrine
(C) raising calcium levels in the blood
(D) regulating diurnal rhythms
(E) producing aldosterone

229. Type 1 diabetes is caused by

(A) the failure of the pancreas to secrete glucagon
(B) the presence of excessive adipose tissue that ties up available
insulin
(C) the failure of the kidneys to move glucose from the blood to the
urine
(D) a loss of sensitivity to insulin by somatic cells
(E) the inability of the pancreas to secrete insulin

230. The secretion of ACTH is in response to

(A) an increased level of epinephrine
(B) a release of TSH from the anterior pituitary
(C) increased blood glucose levels
(D) long-term decreases in metabolic efforts
(E) a release of hormones from the anterior pituitary

231. At a specific point along a neuron that is propagating an action

potential, the sequence of action is
(A) a flood of potassium into the cell; action of the sodium-potassium
pumps; and movement of potassium into the cell
(B) a flood of sodium into the cell; action of the sodium-potassium
pumps; and movement of potassium out of the cell
(C) action of the sodium-potassium pumps; a flood of sodium into the
cell; and movement of potassium into the cell
 (D) a flood of sodium into the cell; movement of potassium out of the
cell; and action of the sodium-potassium pumps
(E) a flood of potassium out of the cell; movement of sodium into the
cell; and action of the sodium-potassium pumps

232. The brain comprises only about 2 percent of total body mass but
consumes about 25 percent of the available glucose. Why?
(A) Although it is only 2 percent of total body mass, the brain actually
contains many more cells than the rest of the body combined.
(B) The brain, because of its control function, is relatively inefficient
when compared to muscle cells.
(C) All neurons must generate huge amounts of energy to maintain
membrane polarity.
(D) Neurons are the primary cell type for maintaining proper blood
glucose levels.
(E) Neurons convert glucose to glycogen for energy storage.

233. Which of the following is best associated with the regulation of

metabolism?
(A) Thyroid
(B) Kidneys
(C) Liver
(D) Thymus
(E) Adenoids

234. The fight-or-flight response arises from the release of what

hormone(s)?
(A) Thyroxine
(B) ACTH and thyroxin
(C) LH and TSH
(D) Epinephrine and norepinephrine
(E) Calcitonin and ACTH
235. A hormone may produce changes within a cell by two mechanisms.
One of these is
(A) binding to surface antibodies attached to mast cells
(B) producing cAMP as a second messenger
(C) neutralizing the effect of calcium influx
(D) increasing neurotransmitter release
(E) increasing the strength of muscle cell contraction

236. The proper sequence of the layers of the meninges, from the outside in,
is
(A) dura mater, arachnoid, pia mater
(B) ventricle, dura mater, pia mater
(C) sulcus, ventricle, pia mater
(D) pia mater, ventricle, sulcus
(E) arachnoid, sulcus, dura mater

237. The portions of the spinal cord that stimulate digestion are the
_______________ nerves.
(A) cervical
(B) sacral
(C) occipital
(D) cranial
(E) lumbar

238. The posterior pituitary is responsible for the secretion of which

hormones?
(A) Glucocorticoids
(B) Aldosterone and epinephrine
(C) FSH and LH
(D) Thyroxine and calcitonin
(E) Oxytocin and ADH

239. The regulation of water concentration in the blood is accomplished by

 (A) melatonin
(B) aldosterone
(C) testosterone
(D) HGH
(E) glucagon

240. Iodine is an essential element because it is associated with what

function?
(A) Control of metabolism
(B) End-plate formation in bone growth
(C) Balance of the autonomic nervous system
(D) Control of membrane permeability
(E) Balance of sugar levels in the blood

241. The function of the choroid plexus in the brain is

(A) connection of the hemispheres
(B) production of CSF
(C) immune surveillance of brain tissue
(D) generation of the white matter
(E) conduction of CSF flow to the subarachnoid space

242. Gamma-aminobutyric acid is

(A) a regulator of HGH production
(B) an enzyme inhibitor associated with HCl production in the
stomach
(C) a neurotransmitter that plays a role in pain perception
(D) an animal hormone that has great structural similarities to plant
hormones
(E) a substance that stimulates the production of calcitonin

243. The master gland of the endocrine system is

(A) the thyroid
(B) the posterior pituitary
(C) the adrenals
 (D) the hypothalamus
(E) the anterior pituitary

244. The portions of the spinal cord that inhibit digestion are the
_______________ nerves.
(A) thoracic
(B) lumbar
(C) cranial
(D) cervical
(E) temporal

245. Steroid hormones control cell action by

(A) binding to a general hormone receptor on the cell surface
(B) producing a second messenger after binding to a specific surface
receptor
(C) binding to a non–membrane-associated nuclear hormone receptor
(D) passing through the cell membrane and increasing the rate of
translation of selected proteins
(E) increasing membrane permeability for protein transport

246. The forebrain consists of all of the following EXCEPT the

(A) cerebrum
(B) pons
(C) thalamus
(D) limbic system
(E) hypothalamus

247. The mechanism of rapid eye movement is best associated with

(A) the fight-or-flight response
(B) a sudden release of ACTH
(C) crossing a threshold for neuron stimulation
(D) excessive levels of iodine
(E) the sleep-wake cycle
248. Which of the following is NOT an effect of long-term stress?
(A) Organ exhaustion
(B) Ion imbalances
(C) Energy depletion
(D) Adrenal exhaustion
(E) Iodine insensitivity

249. Which of the following is a CNS depressant?

(A) Marijuana
(B) PCP
(C) Nicotine
(D) Anabolic steroids
(E) Alcohol

250. An infant suckling his or her mother’s breast causes the release of
_______________ in the mother.
(A) ACTH
(B) bilirubin
(C) HGH
(D) oxytocin
(E) LH

251. Olfactory nerves are best associated with what sense?

(A) Touch
(B) Sight
(C) Hearing
(D) Smell
(E) Taste

252. Which of the following best describes senile dementia?

(A) Loss of reasoning abilities and memory, shortened attention span,
and frequent belligerent behavior
 (B) Loss of short-term memory with a buildup of amyloid plaques in
the brain
(C) Disorientation, forgetfulness, confusion, and loss of speech
(D) Extreme emotional swings, increasing sleepiness, and coma
(E) Enlarged brain ventricles and loss of brain mass

253. Which of the following is NOT a hormone with a cholesterol-derived

structure?
(A) Aldosterone
(B) Testosterone
(C) Estrogen
(D) ACTH
(E) Cortisol

254. An appropriate response for someone entering diabetic shock is

(A) administration of insulin
(B) cardiopulmonary resuscitation
(C) cardiac massage
(D) defibrillation
(E) consumption of a candy bar

255. Insulin is produced within

(A) the α cells within the islets of Langerhans
(B) the entire pancreas
(C) the β cells within the islets of Langerhans
(D) the pituitary
(E) the thymus

256. What is the primary difference between endorphins and enkephalins?

(A) They produce different effects in the body.
(B) One group comprises neurotransmitters, and the other group
comprises hormones.
(C) One group is larger in size than the other.
 (D) One group is lipid based, and the other is composed of amino
acids.
(E) One group is found in humans and the other in lower animals.

257. Which of the following is NOT identified as a taste detected on the

tongue?
(A) Sweet
(B) Seasoned
(C) Savory
(D) Salty
(E) Sour

258. What produces ADH?

(A) Neuroendocrine cells of the hypothalamus
(B) The posterior pituitary
(C) The anterior pituitary
(D) β cells of the islets of Langerhans
(E) The adrenals

259. A term that is the equivalent to stroke is

(A) epileptic seizure
(B) rapid eye movement
(C) hydrocephaly
(D) cerebrovascular accident
(E) concussion

260. Which of the following is NOT true about the hormones released by
the adrenal cortex?
(A) They are released primarily during starvation conditions.
(B) They are associated with upregulating metabolism.
(C) They promote the conversion of proteins to amino acids.
(D) They respond to stress and inflammatory processes.
(E) They help regulate blood glucose levels.
261. The area of the brain best associated with control of respiration and
cardiac output is the
(A) cerebrum
(B) midbrain
(C) medulla oblongata
(D) choroid plexus
(E) pons

262. Which of the following are all associated with control by the
parasympathetic nervous system?
(A) Contraction of the bladder, rectum relaxation, pupil constriction,
and decreased heart rate
(B) Pupil dilation, decreased respiration, inhibition of salivation, and
inhibition of peristalsis
(C) Rectum contraction, increased heart rate, decreased respiration
rate, and pupil constriction
(D) Increased respiration and heart rates, decreased production of
gastric juices, and bladder relaxation
(E) Stimulation of the release of epinephrine, norepinephrine, gastric
juices, and saliva

263. Otoliths are most closely associated with

(A) combining taste and smell during eating
(B) maintaining balance during body movement
(C) the ability to relocate limbs in space without visual confirmation
(D) the perception of both low- and high-frequency sounds
(E) the development of calcium deposits that predispose a person to
gout

264. A visual condition that is best described as an image that focuses in

front of the retina instead of on the retina is
(A) presbyopia
(B) farsightedness
(C) color blindness
 (D) cataracts
(E) nearsightedness

265. “A rapid, unlearned response to an external stimulus” best describes

(A) the fight-or-flight response
(B) regurgitation
(C) micturition
(D) peristalsis
(E) a reflex
 CHAPTER 8

The Circulatory, Lymphatic, and Immune

Systems

266. Of the following, which is the smallest and simplest of the immune
components?
(A) Lymph node
(B) Thymus
(C) Lymph follicle
(D) Lymph nodule
(E) Spleen

267. The best definition for a venule is

(A) a vessel of the circulatory system that lacks muscle tissue and
conducts blood away from the heart
(B) a vessel of the circulatory system that is between an artery and a
capillary in size and conducts lymph toward the heart
(C) a vessel of the lymph system that conducts lymph toward the heart
(D) a vessel of the circulatory system that is between a vein and a
capillary in size and conducts blood toward the heart
(E) a vessel of the lymph system that conducts lymph from the heart

268. The cell type that carries the greatest burden for phagocytic protection
of the body is the
(A) lymphocyte
(B) neutrophil
(C) macrophage
(D) eosinophil
(E) erythrocyte
269. Which of the following best distinguishes serum from plasma?
(A) Serum has a higher concentration of proteins than plasma.
(B) Plasma contains a higher percentage of erythrocytes than serum.
(C) Plasma is the same thing as whole blood, whereas serum lacks the
cellular components.
(D) Whereas plasma contains antibodies, serum contains only the α
and β globulins.
(E) Serum is the same thing as plasma but lacks clotting proteins.

270. Which of the following is NOT descriptive of immunoglobulins?

(A) They are composed of three α chains and one β chain.
(B) They are glycoproteins found in the blood.
(C) They are produced in large quantities by plasma cells.
(D) They are glycoproteins found in lymph.
(E) They neutralize toxins by binding to complementary regions.

271. The primary lymphoid organs include

(A) the thymus and bone marrow
(B) lymph nodes and nodules
(C) the spleen and the thymus
(D) lymph nodes, follicles, and nodules
(E) bone marrow and the thyroid

272. The proper sequence in which blood flows through the heart, starting
at the vena cava, is
(A) right atrium → left atrium → right ventricle → left ventricle
(B) left atrium → left ventricle → right ventricle → right atrium
(C) left ventricle → left atrium → right ventricle → right atrium
(D) right atrium → right ventricle → left atrium → left ventricle
(E) left atrium → right atrium → left ventricle → right ventricle

273. Complement is a series of blood proteins best associated with

(A) the initiation of blood clotting
 (B) the regulation of blood clotting
(C) platelets
(D) cellular lysis
(E) apoptosis

274. The oxygen level is highest in

(A) the pulmonary arteries
(B) capillaries
(C) the pulmonary veins
(D) the vena cava
(E) arterioles

275. Destruction of cancer cells is the responsibility of

(A) helper T cells
(B) macrophages
(C) killer T cells
(D) antibodies
(E) complement

276. Which of the following is NOT a primary function of the lymph

system?
(A) The maintenance of proper fluid balance
(B) The production of antibodies
(C) The transport of large triglycerides
(D) The movement of materials from the tissues to the blood
(E) The transport of proteins

277. A sphygmomanometer is a tool used to measure blood

(A) sugar levels
(B) pressure
(C) oxygenation
(D) protein levels
(E) clotting ability
278. The proper sequence of actions that bring phagocytic cells from
circulation in the blood into infected tissues is
(A) tight binding → rolling adhesion → diapedesis → migration
(B) diapedesis → rolling adhesion → migration → tight binding
(C) migration → rolling adhesion → diapedesis → tight binding
(D) tight binding → diapedesis → migration → rolling adhesion
(E) rolling adhesion → tight binding → diapedesis → migration

279. Erythrocytes are best described as

(A) leukocytes that carry oxygen
(B) thrombocytes that contain iron
(C) bone marrow–derived cells that carry nutrients
(D) lymphocyte-like cells that carry CO2
(E) degenerate cells that contain hemoglobin

280. After antigenic stimulation of a specific B cell, the cell will

(A) undergo lymphoproliferation then differentiation
(B) start to produce membrane-bound antibodies
(C) differentiate into a plasma cell
(D) start the manufacture of antibodies for secretion
(E) differentiate into a memory cell

281. Which of the following does NOT have an especially strong

immunologic presence?
(A) Skin
(B) Respiratory mucosal epithelium
(C) Muscle tissue
(D) Intestinal mucosal epithelium
(E) Blood

282. The proper sequence for the layers of heart tissue, from the outside in,
is
(A) pericardium → epicardium → myocardium → endocardium
 (B) epicardium → endocardium → pericardium → myocardium
(C) myocardium → pericardium → epicardium → endocardium
(D) endocardium → pericardium → myocardium → epicardium
(E) myocardium → epicardium → endocardium → pericardium

283. If a person undergoes plasmapheresis, he or she

(A) may be attempting to help someone with a chronic infection
(B) may be attempting to help someone with hemophilia
(C) probably has a chronic infection
(D) probably has a large fluid regulatory problem
(E) is undergoing therapy for leukemia

284. The proper sequence of valves in which blood flows through the heart,
starting at the vena cava, is
(A) biscupid → pulmonary semilunar → tricuspid → aortic semilunar
(B) pulmonary semilunar → tricuspid → aortic semilunar → bicuspid
(C) tricuspid → aortic semilunar → pulmonary semilunar → bicuspid
(D) tricuspid → pulmonary semilunar → biscupid → aortic semilunar
(E) tricuspid → bicuspid → pulmonary semilunar → aortic semilunar

285. What substance dilates blood vessels, increases tissue pressure, and
can induce hypovolemic shock?
(A) SRS-A
(B) γ-interferon
(C) IL-2
(D) CD4
(E) Histamine

286. In which of the following are foreign antigens best introduced to

lymphocytes for the initiation of the immune response?
(A) The thymus
(B) The thyroid
(C) The kidneys
(D) The spleen
 (E) Bone marrow

287. When blood pressure is monitored, two values are determined. What
occurs within the heart during diastole?
(A) The valves all snap shut.
(B) Both atria and both ventricles relax.
(C) All valves are open.
(D) The left atrium and left ventricle relax, while the right atrium and
right ventricle contract.
(E) The left atrium and left ventricle contract, while the right atrium
and right ventricle relax.

288. Which of the following pairs are most closely related?

(A) Monocyte—lymphocyte
(B) Erythrocyte—leukocyte
(C) Macrophage—monocyte
(D) Eosinophil—basophil
(E) Thrombocyte—granulocyte

289. A genetic blood disorder in which regularly shaped biconcave

erythrocytes fold under conditions of low blood oxygenation is
(A) sickle-cell anemia
(B) pernicious anemia
(C) spherocytosis
(D) hemophilia
(E) leukemia

290. Bacteriophages have been used as a form of antibiotic in protecting

humans from bacterial infections. Why don’t these viruses cause
human disease?
(A) Antibodies in circulation neutralize the viruses.
(B) T cells phagocytose the bacteriophages.
(C) Human cells do not have the proper phage receptors.
(D) Macrophages phagocytose and destroy the bacteriophages.
 (E) The phages are removed from circulation by attaching to the
infecting bacteria.

291. Of the following, which is NOT an autoimmune disorder?

(A) Type 1 diabetes
(B) Rheumatoid arthritis
(C) Hemolytic anemia
(D) Pernicious anemia
(E) Type 2 diabetes

292. Which of the following is NOT considered a granulocyte?

(A) Mast cell
(B) Eosinophil
(C) Basophil
(D) Neutrophil
(E) Lymphocyte

293. Which chemical would interfere with the purpose of platelets?

(A) SRS-A
(B) Histamine
(C) Heparin
(D) Plasminogen
(E) Serotonin

294. Hematopoiesis is a process that occurs in

(A) the spleen
(B) the thymus
(C) lymph nodes
(D) bone marrow
(E) areas of infection

295. The specificity of an antibody is determined by

(A) random gene rearrangements within B-cell progenitors
 (B) antigenic selection of B-cell clones within the bone marrow
(C) clonal selection by macrophages within the bone marrow
(D) B-cell response within lymph nodes
(E) B-cell encounters with foreign antigens

296. The lymph system connects to the circulatory system

(A) within the spleen
(B) in lymph nodes
(C) at the vena cava
(D) at the capillaries in various somatic tissues
(E) within the lungs

297. Which of the following is NOT considered part of the cardiac

conduction system?
(A) The SA node
(B) M cells
(C) Purkinje fibers
(D) The AV bundle
(E) The AV node

298. If a person had a C4 deficiency, what problem(s) would he or she

demonstrate?
(A) Hemophilia
(B) Recurrent infections
(C) Frequent episodes of shock
(D) Pernicious anemia
(E) Heart arrhythmias

299. Oxygen and nutrients reach the myocardium

(A) by diffusion through the endocardium
(B) through two coronary arteries
(C) by diffusion through the pericardium
(D) from the pericardial cavity
(E) through vessels connected to the vena cava
300. Antigen processing and presentation to initiate an antibody response is
best done by
(A) macrophages
(B) endothelial cells
(C) agranulocytes
(D) fibroblasts
(E) granulocytes

301. Cells infected with viruses are best controlled by

(A) macrophages
(B) helper T cells
(C) TS cells
(D) killer T cells
(E) antibodies

302. If whole blood were collected by venipuncture into a tube containing

EDTA or citrate, which of the following could NOT be conducted on
the resulting material in the tube?
(A) A complete blood count
(B) A hematocrit
(C) A differential stain
(D) Quantitation of C3 or C4
(E) Blood clotting time

303. Which of the following antibody classes provides the best protection
against microbial invasion through the intestinal mucosa?
(A) IgM
(B) IgD
(C) IgG
(D) IgE
(E) IgA

304. Which of the following is NOT considered a risk factor for

hypertension?
 (A) Obesity
(B) Smoking
(C) Advanced age
(D) Elevated HDL levels
(E) Elevated sodium levels

305. Which of the following least distinguishes the primary immune

response from the secondary immune response?
(A) A difference in time when a maximum response is presented
(B) Which antibody class is predominant
(C) Which antigen is used to stimulate the responses
(D) The level of the antibody response
(E) The role of memory cells in generating the response

306. Which of the following is NOT considered a contributor to nonspecific

immunity?
(A) Mucus
(B) Tears
(C) NK cells
(D) Memory cells
(E) Urination

307. What cell type is most involved in the swelling and possible shock
following a bee sting?
(A) Mast cell
(B) M cell
(C) Erythrocyte
(D) Neutrophil
(E) Lymphocyte

308. A differential stain is run by diagnosticians to count the various

leukocytes within the blood. Which of the following should always be
at the highest level in a healthy person?
(A) Monocytes
 (B) Lymphocytes
(C) Eosinophils
(D) Basophils
(E) Neutrophils

309. Erythroblastosis fetalis is a blood condition in fetuses caused by

(A) an ABO mismatch between father and mother
(B) an attack of maternal antibodies on fetal erythrocytes
(C) an ABO mismatch between mother and child
(D) a viral infection that precipitates a cross-reactive antibody
response
(E) an Rh mismatch between mother and father

310. Which is the proper sequence of events that produces a blood clot?
(A) Calcium binds prothrombin activator → prothrombin activator
produces thrombin → thrombin produces fibrin → fibrin produces
clot
(B) Prothrombin activator produces thrombin → calcium binds
prothrombin activator → thrombin produces fibrin → fibrin
produces clot
(C) Thrombin produces fibrin → fibrin produces prothrombin activator
→ prothrombin activator produces clot
(D) Fibrin produces thrombin → thrombin produces prothrombin →
prothrombin produces prothrombin activator → prothrombin
activator plus calcium produces clot
(E) Thrombin produces fibrin → fibrin produces prothrombin →
prothrombin produces prothrombin activator → prothrombin
activator plus calcium produces clot
 CHAPTER 9

The Digestive and Excretory Systems

311. The sequence of teeth from the front of the mouth to the rear is
(A) canines → incisors → premolars → molars
(B) molars → premolars → incisors → canines
(C) incisors → canines → premolars → molars
(D) incisors → premolars → canines → molars
(E) canines → premolars → molars → incisors

312. Which of the following is NOT considered a part of the urinary

system?
(A) The ureter
(B) The urethra
(C) The kidneys
(D) The adrenals
(E) The bladder

313. Functions of the digestive system include all but which of the
following?
(A) Mechanical processing of food
(B) Excretion of undigested substances
(C) Absorption of lipids
(D) Replacement of blood cells
(E) Ingestion of substances

314. Which of the following is NOT correct about the control of urination?
(A) A smooth muscle sphincter surrounds the ureter.
(B) A skeletal muscle sphincter surrounds the urethra.
 (C) Two sphincters are located just below the urinary bladder.
(D) A skeletal muscle sphincter is under voluntary control
(E) A smooth muscle sphincter is under involuntary control.

315. What endoscopic diagnostic technique is used to view the interior of

the large intestine?
(A) Enteroscopy
(B) Barium enema
(C) Abdominocentesis
(D) Gastroscopy
(E) Colonoscopy

316. Lipids are absorbed into the _______________ through

the_______________.
(A) circulatory system; stomach
(B) lymph system; large intestine
(C) digestive system; stomach
(D) lymph system; small intestine
(E) circulatory system; small intestine

317. Which of the following is NOT considered part of the kidneys?

(A) Nephrons
(B) The urethra
(C) The cortex
(D) The renal pelvis
(E) The medulla

318. Which of the following is NOT found within pancreatic secretions?

(A) α-amylase
(B) Lipase
(C) β-galactosidase
(D) Trypsin
(E) Phospholipase
319. When a person enters chronic renal failure, which of the following
would likely be observed?
(A) Increased erythrocyte production
(B) Generalized edema
(C) Hyponatremia
(D) Hypouremia
(E) Alkalosis

320. Which of the following is NOT a section of the large intestine?

(A) The cecum
(B) The transverse colon
(C) The sigmoid colon
(D) The vermiform appendix
(E) The duodenum

321. Intrinsic factor allows the absorption of vitamin B12 within the
(A) stomach
(B) transverse colon
(C) jejunum
(D) ileum
(E) vermiform appendix

322. Nephrons can be found within which kidney region(s)?

(A) The renal cortex and pelvis
(B) The renal pelvis and medulla
(C) The renal pyramid and cortex
(D) Bowman’s capsule
(E) The renal medulla

323. Which of the following is NOT a function performed by the liver?

(A) Lipid metabolism
(B) Production of albumin and some blood clotting proteins
(C) Carbohydrate metabolism
 (D) Storage of water-soluble vitamins
(E) Storage of iron and vitamin B12

324. Which of the following is NOT removed from the blood by the
kidneys?
(A) Urea
(B) Wastes from drug metabolism
(C) Uric acid
(D) Creatinine
(E) Wastes from protein synthesis

325. When a gallstone is passed, where does it go?

(A) To the bladder
(B) To the duodenum
(C) To the pancreas
(D) To the liver
(E) To the stomach

326. Amylase is released into the digestion tract in which region(s)?

(A) The large intestine and vermiform appendix
(B) The mouth and stomach
(C) The esophagus
(D) The mouth and small intestine
(E) The large intestine

327. Which of the following represents the correct sequence of the passage
of urine in a nephron?
(A) Bowman’s capsule → loop of Henle → distal tubule → collecting
tubule
(B) Loop of Henle → Bowman’s capsule → distal tubule → collecting
tubule
(C) Bowman’s capsule → loop of Henle → collecting tubule → distal
tubule
 (D) Collecting tubule → proximal convoluted tubule → distal tubule
→ Bowman’s capsule
(E) Bowman’s capsule → distal tubule → loop of Henle → proximal
convoluted tubule

328. Bile is composed of at least which of the following combinations of

substances?
(A) Cholesterol, bile salts, and HCl
(B) Water, bilirubin, and cholesterol
(C) Bile salts, nitrogenous wastes, and bilirubin
(D) Amylase, glycogen, and bile salts
(E) Trypsin, bile salts, and glycogen

329. The mechanism that removes small nutrients, ions, and water from the
glomerular filtrate is called
(A) tubular reabsorption
(B) tubular secretion
(C) urinary tension
(D) passive diffusion
(E) reverse osmotic gradient formation

330. Which of the following is NOT a function of the material(s) produced

by parietal cells within the stomach?
(A) Activation of pepsinogen
(B) Killing of microorganisims
(C) Formation of gastric mucus
(D) Absorption of vitamin B12
(E) Denaturation of proteins

331. Salivation is important for the digestive process. Which of the

following is NOT true about saliva or salivation?
(A) Saliva contains antibodies and lysozyme.
(B) A typical adult produces about 1 L of saliva daily.
(C) Saliva contains mucin, amylase, and bicarbonate.
 (D) Saliva is composed of about 99.5 percent water.
(E) There are four pairs of salivary glands: parotid, submandibular,
pharyngeal tonsils, and sublingual.

332. The term countercurrent multiplier mechanism refers to

(A) a laboratory technique used to evaluate protein concentration in
urine
(B) a mechanism by which lipids are absorbed within the intestinal
tract
(C) a mechanism used to create a concentration gradient within the
loop of Henle
(D) a mechanism used by the autonomic nervous system to control
peristalsis
(E) a model used within the stomach to produce significant quantities
of HCl

333. Which of the following is the first step of the involuntary phase of
swallowing?
(A) The soft palate rises to close off the nasal passages.
(B) Muscles close off the esophagus.
(C) The tongue pushes the chewed bolus into the pharynx.
(D) The epiglottis closes off the trachea and opens the esophagus.
(E) The rate of secretion by the salivary glands increases.

334. Which of the following is true concerning mechanisms involved within

the loop of Henle?
(A) Water enters the urine in the descending portion.
(B) Sodium and chlorine ions leave the urine in the ascending loop.
(C) Water leaves the urine in the ascending portion.
(D) Proteins are absorbed back into the blood in both the ascending
and descending portions.
(E) Water, sodium ions, and potassium ions leave the urine in the
descending portion.
335. Which of the following is NOT descriptive of the small intestine?
(A) Nutrient absorption takes place within the small intestine.
(B) Brush border epithelial cells are involved in carbohydrate
digestion.
(C) The lumen is lined with plicae covered with villi to increase
adsorption.
(D) Peristalsis of the small intestine is under autonomic control.
(E) Digestion in the small intestine begins in the jejunum.

336. Which of the following best describes the function or structure of the
stomach?
(A) Food is mechanically processed into chyme for three to four hours.
(B) The lining of the stomach is smooth to increase absorption of
nutrients and water.
(C) Food enters the stomach through the pyloric sphincter.
(D) Gastric pits are lined with antibody-containing mucus to protect
the body from bacterial entry.
(E) Duodenal ulcers may become colonized with bacteria that prevent
healing.

337. Alcohol intake increases urination by

(A) simply increasing water intake as well
(B) interfering with the function of ADH
(C) altering the ion balance in the nephrons
(D) blocking the reabsorption of proteins and thus altering fluid
balance
(E) interfering with the production of ADH in the adrenals

338. Which of the following is responsible for manufacturing bile?

(A) The spleen
(B) The pancreas
(C) The liver
(D) The gallbladder
(E) The stomach
339. What is the physiological response when someone increases his or her
water intake?
(A) The adrenals increase the rate of water reabsorption in the kidneys.
(B) The hypothalamus and anterior pituitary decrease the rate of water
reabsorption in the kidneys.
(C) The pancreas releases insulin to increase sugar and water uptake
by all cells.
(D) The glomeruli in the kidneys decrease the effectiveness of
retaining proteins in the blood, thus increasing urinary output.
(E) The autonomic nervous system increases the rate of sweat
production as a means of maintaining fluid balance.

340. Which of the following is true about the absorption of carbohydrates?

(A) Polysaccharides are broken down into simple sugars in the
intestinal lumen and then passively diffuse into the lymph.
(B) Proteins are broken down into monosaccharides in the intestinal
lumen and are then brought into the epithelial cells by active
transport.
(C) Complex carbohydrates are brought into epithelial cells by active
transport and then enter the lymph by facilitated diffusion.
(D) Simple sugars enter epithelial cells by active transport, exit these
cells by facilitated diffusion, and then enter capillaries by simple
diffusion.
(E) Since the sugar concentration is highest in the intestinal lumen and
lowest in the blood, simple diffusion is all that is needed to get the
sugar into the blood.

341. The sequence of the process needed for lipid absorption is

(A) digestion by lipases → emulsification by bile salts → formation of
chylomicrons → secretion by epithelial cells
(B) formation of chylomicrons → secretion by epithelial cells →
movement into lymph → digestion by lipases
(C) emulsification by bile salts → formation of chylomicrons →
digestion by lipases → movement into lymph
 (D) digestion by lipases → formation of chylomicrons → movement
into lymph → absorption of micelles
(E) emulsification by bile salts → digestion by lipases → formation of
chylomicrons → secretion by epithelial cells

342. Materials exit the blood and enter the nephron

(A) in the Bowman’s capsule
(B) in the proximal convoluted tubule
(C) in the ascending portion of the loop of Henle
(D) in the medullary pyramid
(E) in the afferent arteriole

343. The sequence of layers of the intestine, from the lumen outward, is
(A) submucosa → mucosa → serosa → muscularis → mesentery
(B) serosa → mucosa → submucosa → mesentery → muscularis
(C) mucosa → submucosa → muscularis → serosa → mesentery
(D) mesentery → submucosa → mucosa → serosa → muscularis
(E) mucosa → submucosa → serosa → muscularis → mesentery

344. The kidneys have a role in all of the following EXCEPT

(A) excreting wastes and toxic substances
(B) maintaining body fluid pH
(C) contributing to homeostasis
(D) disposing of bilirubin through the urine
(E) maintaining fluid balance and blood pressure
 CHAPTER 10

The Muscle and Skeletal Systems

345. Which of the following correctly describes smooth muscle?

(A) Smooth muscle tissue is only localized along the digestive system.
(B) Smooth muscle cells are striated and under involuntary control.
(C) Smooth muscle tissues are best associated with bony structures.
(D) Smooth muscle tissues provide for long-term slow contractions.
(E) Smooth muscle contractions are under voluntary control.

346. Which of the following are NOT bones in the skull?

(A) The maxilla and mandible
(B) The palatine and sphenoid
(C) The tarsals and metatarsals
(D) The parietal and occipital
(E) The ethmoid and zygomatic

347. Which of the following muscle combinations work synergistically?

(A) The sartorius and hamstring
(B) The biceps and triceps
(C) The pectoralis major and trapezius
(D) The quadriceps and biceps
(E) The hamstring and gastrocnemius

348. Which of the following is NOT true concerning the vertebrae?

(A) There are seven cervical vertebrae.
(B) The coccyx is composed of seven fused bones.
(C) The lumbar region is located below the thoracic region.
(D) The sacrum connects the coccyx to the lumbar vertebrae.
 (E) The vertebrae protect portions of the CNS.

349. A fibrous joint is best described as

(A) immovable
(B) a joint similar to the knee or elbow
(C) slightly moveable
(D) a joint similar to that which connects the sternum to adjacent
cartilage
(E) highly moveable

350. The best description of a sarcomere is that it

(A) is the place where a bone attaches to muscle tissue
(B) is another name for a muscle cell
(C) contains the postsynaptic receptors of a muscle
(D) stores calcium needed for muscle contraction
(E) is the contractile unit of the myofibril

351. Which of the following is NOT a primary function of the skeletal

system?
(A) It provides support for movement.
(B) It is essential for cellular metabolism.
(C) It is the primary reservoir for calcium and phosphate.
(D) It provides for hematopoiesis.
(E) It protects the organs.

352. The sarcoplasmic reticulum is

(A) protected by the skull
(B) essential for muscle contraction
(C) involved in protein synthesis and transport
(D) a cellular joining structure that provides for muscle fiber integrity
and strength
(E) essential in the transport of ATP from the mitochondria to the
contractile unit in muscle cells
353. Spongy bone is best associated with
(A) bone loss
(B) the structure of the diaphysis
(C) the medullary cavity
(D) the proximal epiphysis
(E) the periosteum

354. Which of the following is NOT closely associated with the knee?
(A) Ligaments
(B) The patella
(C) The fibrous joint
(D) Meniscus
(E) The femur

355. Which of the following is used to power muscle cells immediately

after the initial supply of ATP is exhausted?
(A) Glucose
(B) Creatine phosphate
(C) Fatty acids
(D) Glycogen
(E) Starch

356. The _______________ is the connective tissue that contains

osteoclasts.
(A) epiphysis
(B) yellow marrow
(C) haversian canal
(D) compact bone
(E) periosteum

357. The muscles best associated with peristalsis of the digestive system are
controlled by
(A) the parasympathetic nervous system
 (B) the cerebrum
(C) the sympathetic nervous system
(D) both the sympathetic and parasympathetic nervous systems
(E) the cerebrum and cerebellum

358. During adolescent development, bones elongate by

(A) formation of bone tissue just under the joint cartilage
(B) deposition of spongy bone within the marrow cavity
(C) formation of bone tissue under the cartilage epiphyseal plate
(D) deposition of dense bone along the marrow cavity
(E) deposition of collagenous fibrocartilage at the ends of the marrow
cavity

359. Which of the following is the best description of a tendon?

(A) A connective tissue that encloses synovial fluid
(B) A bone-derived tissue that connects bone to bone
(C) A highly vasculated tissue that connects bone to muscle
(D) A collagenous material that connects bone to bone
(E) A connective tissue that connects bone to muscle

360. The thin filament of a sarcomere is composed primarily of

(A) titin
(B) tropomyosin
(C) actin
(D) troponin
(E) myosin

361. Osteoarthritis differs from rheumatoid arthritis in that

(A) the former is caused by wear, whereas the latter is caused by
infection
(B) the former retains overall integrity of the joint, whereas the latter
produces permanent deformation
(C) the former is initiated by mechanical mechanisms, whereas the
latter is an autoimmune disorder
 (D) the former affects primarily synovial joints, whereas the latter
primarily affects fibrocartilage
(E) the former involves adjacent ligaments, whereas the latter does not

362. Cardiac muscle cells, when grown in the lab in petri dishes, begin to
beat in a synchronized fashion when they make contact with each
other. Why might this be so?
(A) The cells start to form nerve connections between themselves.
(B) The cells release ATP into the surrounding medium in a
synchronized fashion.
(C) The cells release into the surrounding medium calcium ions that
synchronizes contraction.
(D) The cells connect to each other by gap junctions upon making
contact.
(E) When one cell starts to contract, any cell in contact responds to the
sudden motion as a physically gated stimulus.

363. What is the sequence of the repair of a bone following fracture?

(A) Callus forms → hematoma forms → osteoclasts remove fragments
→ osteoblasts replace bone material
(B) Osteoclasts remove debris → osteocytes form haversian canals →
hematoma forms → callus forms
(C) Hematoma forms → callus forms → osteocytes form haversian
canals → osteoblasts replace bone material
(D) Callus forms → osteoclasts remove debris → hematoma forms →
osteoblasts form haversian canals
(E) Hematoma forms → callus forms → osteoclasts remove debris →
osteoblasts replace bone material

364. Which of the following is NOT true of the human rib cage?
(A) Ribs 8 through 10 are known as false ribs.
(B) All ribs are attached to thoracic vertebrae.
(C) The spaces between the ribs are called intervertebral spaces.
(D) Ribs 11 and 12 are not connected to the sternum.
(E) The rib cage is considered part of the respiratory system.
365. Which of the following is true about the interrelatedness of bone and
skeletal muscle?
(A) Muscles connect through tendons to relatively immobile origins.
(B) Muscles produce motion by pushing against the tendon origin.
(C) Joints rotate when synovial pressures increase suddenly.
(D) Muscles connect through tendons to relatively immobile
insertions.
(E) Muscles connect to a single bone at both ends via collagenous
fibrocartilage.

366. The axial skeleton consists of all of the following EXCEPT the
(A) skull
(B) ribs
(C) vertebrae
(D) sternum
(E) femurs

367. A person with McArdle disease has a deficiency in glycogen storage.

How would this disease manifest itself?
(A) Onset of rapid fatigue during exercise
(B) Adult-onset (type 2) diabetes
(C) Muscle atrophy because of the inability to contract
(D) Very short stature and increased bone density
(E) Rapid cartilage degeneration and early-onset arthritis

368. The analogous structures to the tibia and fibula are the
(A) carpal and metacarpal
(B) radius and ulna
(C) humerus and scapula
(D) sacrum and coccyx
(E) clavicle and scapula

369. Which of the following is probably NOT appropriate for someone with
osteoporosis?
 (A) Calcium supplementation
(B) Moderate exercise
(C) Estrogen replacement for women
(D) Contact sports
(E) Stretching

370. The muscle that bends the backbone forward is the

(A) rectus abdominis
(B) latissimus dorsi
(C) gluteus maximus
(D) external oblique
(E) serratus anterior
 CHAPTER 11

The Respiratory System

371. What is the function of the septal cells found within the alveoli of the
lungs?
(A) They provide immune surveillance, protecting the lungs from
infection.
(B) They secrete surfactants.
(C) They comprise the bulk of the alveolar cells involved in gas
exchange.
(D) They serve as a barrier between the circulatory system and the
respiratory system.
(E) They serve to remove dust and dirt particles within the lungs.

372. The proper sequence of structures that inspire air encounters en route
to the circulatory system is
(A) pharynx → larynx → trachea → bronchi → bronchioles → alveoli
(B) alveoli → larynx → pharynx → bronchioles → bronchi → trachea
(C) pharynx → trachea → larynx → bronchi → bronchioles → alveoli
(D) trachea → pharynx → larynx → bronchioles → bronchi → alveoli
(E) pharynx → bronchi → bronchioles → trachea → alveoli → larynx

373. Which of the following is NOT a commonly classified breathing type?

(A) Quiet
(B) Deep
(C) Forced
(D) Erratic
(E) Shallow
374. Which of the following is the best description for inspiratory reserve
volume?
(A) The amount of air within the lungs at rest
(B) The amount of air remaining in the lungs after forced exhalation
(C) The maximum amount of air that can forcefully be brought into the
lungs
(D) The difference between the amount of the air in the lungs at rest
and the amount brought in by use of muscles
(E) The amount of air expelled by muscles after being at rest

375. Which, if any, of the following is NOT associated with the protection
of the lungs?
(A) Nasal turbinates
(B) Alveolar macrophages
(C) Ciliary escalator
(D) Mucus coating the air passages
(E) All of the above

376. Boyle’s law is important in understanding the breathing mechanism. It

states that
(A) for any given temperature, air pressure remains constant at sea
level
(B) blood pressure and atmospheric pressure are directly correlated
(C) there is an inverse relationship between pressure and volume for a
given amount of air
(D) gas flow from the atmosphere to the blood and from the blood into
the atmosphere is independent
(E) the flows of the different atmospheric gasses are all linked

377. The component(s) of the conductive segment of the respiratory system

that lack(s) cartilage include(s) the
(A) pharynx
(B) trachea and bronchi
(C) pharynx, trachea, and bronchi
 (D) trachea and bronchioles
(E) bronchioles

378. The origin of CO2 in the blood is

(A) the natural equilibrium conversion process from O2
(B) glycolysis and the Krebs cycle in tissue cells
(C) the product from acting as the final electron acceptor in oxidative
phosphorylation
(D) passive diffusion from the atmosphere
(E) conversion from bicarbonate in the blood

379. The autonomic control of breathing is centered in the

(A) AV node
(B) medulla oblongata
(C) cerebellum
(D) hypothalamus
(E) respiratory gyrus of the cerebrum

380. Which antibody class is best associated with mucus secretions in the
respiratory tract?
(A) IgE
(B) IgM
(C) IgD
(D) IgA
(E) IgG

381. What is the fate of CO2 acquired in the tissue capillaries when it enters
the blood?
(A) More than 90 percent enters erythrocytes, and about 25 percent of
that binds to hemoglobin.
(B) All of it remains in the plasma as dissolved CO2.
(C) Less than 10 percent remains in the plasma as CO2, while the
remainder disassociates into H+ and .
 (D) All of it is converted to within the erythrocytes, which is
then released by passive diffusion into the plasma.
(E) About 25 percent returns into the tissues by passive diffusion as the
blood returns to the lungs; the remainder is exhaled.

382. Which of the following conditions generally does NOT interfere with
gas exchange within the alveoli?
(A) Pulmonary tuberculosis
(B) Chemically induced pneumonia
(C) Emphysema
(D) Bacterial pneumonia
(E) Lung cancer

383. If the atmosphere contains 78 percent nitrogen and 21 percent oxygen,

about what percentage of the total blood gasses is nitrogen?
(A) 78 percent
(B) 28 percent
(C) 67 percent
(D) Less than 2 percent
(E) 95 percent

384. During deep breathing, which of the following muscles is (are) most
involved?
(A) The external intercostals
(B) The diaphragm and serratus anterior
(C) The external and internal intercostals
(D) The diaphragm
(E) The diaphragm, internal intercostals, and external intercostals

385. The movement of respiratory mucus helps protect the respiratory tree.
Which of the following is true about this mechanism?
(A) All of the mucus is swept upward to be swallowed or spit out.
(B) Mucus below the larynx is swept downward, and mucus above the
larynx is swept upward.
 (C) Mucus above the pharynx is swept downward, and mucus below
the pharynx is swept upward.
(D) Movement of the mucus is random to prevent attachment to the
epithelium by respiratory pathogens.
(E) The movement of the mucus helps ensure that both the upper and
lower respiratory tracts remain sterile as maintained by
macrophages.

386. The respective partial pressures (in mm Hg) for oxygen (pO2) and
carbon dioxide (pCO2) in the tissues are
(A) pO2 = 40 mm; pCO2 = 45 mm
(B) pO2 = 40 mm; pCO2 = 100 mm
(C) pO2 = 100 mm; pCO2 = 60 mm
(D) pO2 = 100 mm; pCO2 = 40 mm
(E) pO2 = 40 mm; pCO2 = 20 mm

387. Which of the following provides the best description of the anatomy of
the lungs?
(A) Three left lobes and two right lobes resting on the diaphragm, all
of which is surrounded by pleural membranes
(B) Three right lobes and two left lobes surrounded by pleural
membranes and resting on the diaphragm
(C) Two left lobes and three right lobes surrounding the heart, and all
surrounded by pleural membranes
(D) Three left lobes and two right lobes surrounding the heart and
resting on the diaphragm, all of which is surrounded by pleural
membranes
(E) Three right lobes and two left lobes surrounded by pleural
membranes, surrounding the heart, and all resting on the
diaphragm

388. Stimulation of chemoreceptors can affect lung function. Which of the

following does NOT occur when alveolar CO2 levels get too high?
 (A) Bronchodilation increases air flow to the alveoli.
(B) The respiration rate increases.
(C) The elevated CO2 levels produce the yawning reflex.
(D) The pO2 levels drop proportionately.
(E) The rate of gas exchange in the alveoli increases.

389. Irritation of which of the following areas does NOT produce a

coughing reflex?
(A) The larynx
(B) The oropharynx
(C) The primary bronchi
(D) The trachea
(E) The secondary bronchi

390. Chronic obstructive pulmonary disease is defined as a condition

representing a loss of more than 50 percent of expected breathing
capacity. Which of the following is NOT included in this definition?
(A) Chronic asthma
(B) Chronic bronchiolitis
(C) Pulmonary emphysema
(D) Chronic bronchitis
(E) Bacterial pneumonia

391. The nasal turbinates have several roles within the respiratory system.
Which of the following is NOT one of those roles?
(A) To moisten the air entering the lungs
(B) To recover water that might be lost during exhalation
(C) To cool the air entering the lungs
(D) To carry air to the olfactory centers
(E) To trap dust and larger infectious materials
 CHAPTER 12

The Skin

392. The skin has sensory organs that can detect all of the following
EXCEPT
(A) cold
(B) stretching
(C) pressure
(D) pain
(E) touch

393. The sequence of skin layers, arranged from the inside to the surface, is
(A) dermis → hypodermis → stratum corneum → stratum basale
(B) hypodermis → dermis → stratum basale → stratum corneum
(C) stratum basale → hypodermis → dermis → stratum corneum
(D) stratum basale → stratum corneum → hypodermis → dermis
(E) stratum corneum → hypodermis → dermis → stratum basale

394. Which of the following is the most life-threatening form of skin

cancer?
(A) A mole
(B) A squamous cell carcinoma
(C) A melanoma
(D) A basal cell carcinoma
(E) An adenoma

395. Which of the following is NOT descriptive of an eccrine gland?

(A) Eccrine glands are located primarily in the armpits and groin area.
(B) There are approximately three million eccrine glands.
 (C) Eccrine glands secrete water containing small amounts of sodium,
chlorine, and potassium ions.
(D) Eccrine glands secrete lysozyme.
(E) Eccrine glands are essential for cooling the body.

396. Skin cells are derived from columnar epithelial germinal cells. Into
what form do they terminally differentiate?
(A) Cuboidal
(B) Terminal columnar
(C) Keratinized cuboidal
(D) Keratinized squamous
(E) Foliate

397. Body temperature, as adjusted by skin glands and dermal blood

vessels, is ultimately controlled by
(A) the pituitary
(B) free nerve endings
(C) the spinal cord
(D) Merkel disks
(E) the hypothalamus

398. Which of the following is NOT associated with protection provided by

the skin?
(A) Sebum
(B) Lysozyme
(C) Synthesis of vitamin D
(D) Sensory reflexes
(E) Surface salt deposits

399. Following a bleeding break in the skin, which of the following is the
proper sequence of events that lead to its repair?
(A) Debris removal → clot formation → fibroblast proliferation →
inflammation → regeneration
 (B) Inflammation → clot formation → regeneration → fibroblast
proliferation → debris removal
(C) Clot formation → fibroblast proliferation → debris removal →
inflammation → regeneration
(D) Clot formation → inflammation → fibroblast proliferation →
debris removal → regeneration
(E) Clot formation → debris removal → inflammation → fibroblast
proliferation → regeneration

400. Following any break in the skin, which antibody isotype provides the
bulk of protection during healing?
(A) IgG
(B) IgM
(C) IgE
(D) IgD
(E) IgA

401. Which of the following provides the best description of the dermis?
(A) The layer of skin consisting primarily of keratinocytes and
melanocytes
(B) The outer layer of skin that is rich in blood vessels and connective
tissue
(C) A layer below the epidermis that is full of blood vessels,
melanocytes, and keratinocytes
(D) The layer of skin composed of columnar cells, cuboidal cells, and
keratinized squamous epithelium
(E) A layer below the epidermis consisting of an extracellular matrix,
fibroblasts, macrophages, and other leukocytes

402. Which of the following are best associated with thermoregulation?

(A) Arrector pili
(B) Sebaceous glands
(C) Apocrine glands
(D) Fingernails and toenails
 (E) Meissner corpuscles

403. Which of the following does NOT accelerate with age?

(A) Slower wound healing
(B) Loss of melanocytes
(C) Decreasing cell regeneration
(D) Increasing elasticity in the dermis
(E) Loss of collagen in the dermis

404. Which of the following is NOT secreted on the skin by glands?

(A) Ammonia
(B) Salts
(C) Lipids
(D) Antibodies
(E) Amylase

405. The primary reason for baldness is

(A) stress
(B) mite infection of the hair follicle
(C) muscle tension
(D) hormones
(E) poor grooming

406. Normal skin color is imparted by

(A) melanin and hemoglobin
(B) carotene and melanin
(C) hemoglobin, melanin, and carotene
(D) melanin
(E) salts, melanin, and bilirubin

407. Which of the following pairs is NOT a correct association?

(A) Merkel disks and sense of touch
(B) Meissner corpuscles and sense of movement of the hair shaft
 (C) Free nerve endings and sense of temperature
(D) Pacinian corpuscles and sense of pressure
(E) Free nerve endings and sense of pain

408. Fingernail and toenail growth occurs because of

(A) protein synthesis in the nail bed
(B) osteoclasts laying down nail matrix in the lunula
(C) epithelial cell division
(D) synthesis of hardened sebum
(E) polysaccharide synthesis and export by epithelial cells

409. The skin has been described as the largest organ of the body. Which of
the following is NOT true?
(A) Skin provides protection and defense.
(B) Skin is essential for maintaining water balance.
(C) Skin assists in maintaining homeostasis.
(D) Skin serves as a major sensory organ.
(E) Skin provides a mechanism for synthesis of vitamins A and D.

410. What is the function of the papillae in the dermis?

(A) To aid in homeostasis by helping maintain heat balance
(B) To serve as an anchor for the epidermis
(C) To aid in homeostasis by helping to maintain fluid balance
(D) To enhance immunity by increasing immune surveillance by
macrophages
(E) To provide nutrients to the squamous epithelium

411. Which of the following is true concerning the role of the dermis in
nutrition?
(A) The skin helps synthesize molecules later activated in the liver that
aid in calcium absorption in the intestine.
(B) Cells within the skin manufacture growth factors that provide for
improved connective tissue elasticity throughout the body.
(C) Significant energy is stored in the dermis in the form of
collagenous proteins.
(D) Significant levels of essential minerals are absorbed into the
dermis after passing through the epidermis.
(E) The capillary beds within the dermis provide for additional levels
of gas exchange with the atmosphere.
 CHAPTER 13

The Reproductive System and Development

412. The purpose of the acrosome on the tip of sperm cells is

(A) to provide the energy to burrow through the zona pellucida
(B) to provide the molecular sensors for chemotaxis to the ovum
(C) to provide enzymes that permit tunneling through the zona
pellucida
(D) to provide the energy required to move the flagellum toward the
ovum
(E) to provide protection for the sperm in the hostile environment
encountered en route to the ovum

413. The proper sequence of stages in embryonic development is

(A) fertilization → cleavage of blastomeres → morula → blastocyst
(B) cleavage of blastomeres → fertilization → morula → blastocyst
(C) fertilization → blastocyst → morula → cleavage of blastomeres
(D) morula → cleavage of blastomeres → fertilization → blastocyst
(E) fertilization → blastocyst → cleavage of blastomeres → morula

414. The simplest complete summary for the formation of gametes is

(A) 2n → 4n → 2n
(B) 1n → 2n → 4n
(C) 1n → 2n → 4n → 2n → 1n
(D) 2n → 4n → 2n → 1n
(E) 2n → 1n

415. Which of the following is the structure usually involved in an ectopic

pregnancy?
 (A) The vagina
(B) The fallopian tube
(C) The perimetrium
(D) The endometrium
(E) The ovary

416. Which of the following is NOT a tissue derived from the embryonic
ectoderm?
(A) Tooth enamel
(B) The posterior pituitary gland
(C) Skin epidermis
(D) The retina of the eye
(E) The thymus

417. Which is the correct sequence for the development of the CNS during
embryogenesis?
(A) Notochord → neural groove → neural fold → neural tube
(B) Neural groove → neural fold → neural tube → notochord
(C) Notochord → neural tube → neural fold → neural groove
(D) Neural fold → neural groove → notochord → neural tube
(E) Neural groove → neural fold → neural tube → notochord

418. Which of the following is the best description of the allantois?

(A) Remnants of membranes and placenta
(B) The extraembryonic membrane that supports fetal development
(C) The vessel that carries blood from the placenta to the fetus
(D) The extraembryonic membrane that forms the bladder
(E) The vessel that carries blood from the fetus to the placenta

419. The proper sequence of the development of the sperm is

(A) primary spermatocyte → secondary spermatocyte → spermatid →
Sertoli cell
(B) spermatid → primary spermatocyte → secondary spermatocyte →
Sertoli cell
 (C) secondary spermatocyte → primary spermatocyte →
spermatogonium → spermatid
(D) spermatogonium → primary spermatocyte → secondary
spermatocyte → spermatid
(E) Sertoli cell → spermatogonium → secondary spermatocyte →
primary spermatocyte → spermatid

420. A female has about ________________ primary oocytes at birth, of

which about _______________ will be released by ovulation in her
lifetime.
(A) 10,000; 500
(B) 500,000; 500
(C) 20,000; 200
(D) 100,000; 100
(E) 5,000; 500

421. Which of the following is the best description of a polar body?

(A) A mature female gamete
(B) A haploid cell that produces primary oocytes
(C) A degenerate cell resulting from meiosis
(D) A haploid cell in a secondary follicle that is released at ovulation
(E) A diploid cell that gives rise to the secondary oocyte

422. Identical twins are a result of

(A) double fertilization of a single ovum
(B) separate fertilization of two different ova
(C) fusion of two separately fertilized ova
(D) division of a single fertilized ovum into two zygotes
(E) division of a single ovum with each daughter cell fertilized
separately

423. Which of the following is NOT a tissue derived from the embryonic
mesoderm?
(A) Digestive tract mucosa
 (B) Bone marrow
(C) Gonads
(D) Lymph vessels
(E) Connective tissue

424. Sperm are formed in the

(A) epididymis
(B) seminiferous tubules
(C) prostate gland
(D) vas deferens
(E) bulbourethral gland

425. The follicular phase of the menstrual cycle includes

(A) a uterine proliferative phase, a menstrual phase, and a rise in
estrogen and LH
(B) a menstrual phase, a secretory phase, and a rise in progesterone
(C) ovulation and a rise in progesterone and estrogen
(D) a rise in LH, FSH, estrogen, and progesterone
(E) a rise in progesterone and a secretory phase

426. The components of the sperm include all of the following EXCEPT
(A) microtubules
(B) flagellum
(C) endoplasmic reticulum
(D) acrosome
(E) mitochondria

427. Marked jaundice in an infant at birth is most commonly a sign of

(A) Rh incompatibility with the mother
(B) an autoimmune disorder
(C) an ABO mismatch with the mother
(D) an Rh mismatch with the mother
(E) the infant inheriting the father’s tissue type
428. Which of the following is NOT a tissue derived from the embryonic
endoderm?
(A) Sweat glands
(B) The anterior pituitary
(C) Muscle tissue
(D) Lung alveoli
(E) The thyroid gland

429. Testosterone is produced by

(A) Sertoli cells in the seminiferous tubules
(B) spermatogonia within the seminiferous tubules
(C) the prostate
(D) the bulbourethral gland
(E) interstitial cells of the seminiferous tubules

430. A newborn infant has an immature immune system but is initially

protected by
(A) antibodies passed on from the mother in her breast milk
(B) helper T cells passed on from the mother through the placenta
(C) antibody-producing cells acquired during the birth process from
the umbilical cord
(D) maternal macrophages occupying fetal lymph nodes
(E) antibodies passed on from the mother through the placenta

431. Which of the following hormones plays no role in a mother’s lactation

following birth?
(A) Oxytocin
(B) Estrogen
(C) Progesterone
(D) Prolactin
(E) Testosterone

432. Which of the following is NOT a correct pairing of extraembryonic

membranes and their function?
 (A) amnion—produces cushioning fluid for the fetus
(B) myometrium—helps form the placenta
(C) allantois—helps form the umbilical cord
(D) yolk sac—initially forms fetal blood cells
(E) chorion—assists in gas exchange between the mother and fetus

433. During embryonic development, at which point can a heartbeat

initially be detected?
(A) Month 3
(B) Week 4
(C) Week 8
(D) Month 5
(E) Month 4

434. When fingers initially form in utero, they are connected by skin
“webbing.” Why is this webbing no longer present at birth?
(A) There are no blood vessels in the webbing, so the cells die off.
(B) The buildup of fetal urine within the amnion removes these cells.
(C) As the fetus starts to move the fingers, the thin web tissue tears and
degrades.
(D) The web cells undergo programmed apoptosis.
(E) Maternal antibodies in the amnion attack and remove these
temporary cells.

435. The luteal phase of the menstrual cycle is best associated with
(A) progressively increasing FSH and LH levels
(B) the secretory phase of the uterine cycle
(C) menses and uterine proliferation
(D) a spike of estrogen, LH, and FSH
(E) ovarian follicle maturation
 CHAPTER 14

Genetics

436. What is the best way to express the difference between a genotype and
a genome?
(A) Two organisms may vary in genotype due to differences in DNA
sequences but have the same genome because they have the same
genes.
(B) One organism may have one genome but two genotypes if they are
diploid.
(C) Eukaryotes have genomes; prokaryotes have genotypes.
(D) Genotype represents the sequence of gene loci, whereas genome
means the sequence of DNA bases.
(E) Eukaryotes have genotypes; prokaryotes have genomes.

437. Which of the following is true about a human male’s karyotype?

(A) There are 23 homologous chromosomes.
(B) Banding patterns for all chromosomes in a single nucleus are
identical.
(C) Banding patterns for all autosomes in a single nucleus are
identical.
(D) All chromosomes are in matching pairs.
(E) There are 22 homologous chromosome pairs.

438. Klinefelter syndrome is indicated by an XXY sex chromosome

combination. This abnormality is due to
(A) gene deletion
(B) gene duplication
(C) nondisjunction
(D) gene translocation
 (E) infertility

439. The human ABO blood groups are under ______________ inheritance
control.
(A) simple dominance
(B) codominance
(C) partial dominance
(D) incomplete dominance
(E) epistatic

440. Which of the following is NOT true concerning the process of

meiosis?
(A) Alternate forms of the genes are shuffled.
(B) Parental DNA is divided and distributed to gametes.
(C) The number of chromosomes is changed from diploid to haploid.
(D) Offspring are provided with new gene combinations.
(E) Meiosis is a process that occurs only in the ovaries, not in the
testes.

441. _______________ is a genetic disorder in which the individual has a

mutation in an ion channel protein.
(A) Tay-Sachs
(B) Hemophilia
(C) Sickle-cell disease
(D) Cystic fibrosis
(E) Phenylketonuria

442. When a parent cell gives rise to four genetically different daughter
cells, the process is known as
(A) a series of mutations
(B) meiosis
(C) cloning
(D) mitosis
(E) genetic engineering
443. A father with type A blood and a mother with type B blood will
(A) always have children with type A blood
(B) always have children with type B blood
(C) never have children with type O blood
(D) more often than not have children with type O blood
(E) have children of all blood types, depending on the parental
genotypes

444. By convention, a genotype designation of RR would indicate

(A) homozygous dominant on any chromosome
(B) heterozygous on male sex chromosomes
(C) homozygous recessive on autosomes
(D) heterozygous on autosomes
(E) hemizygous on female sex chromosomes

445. Which of the following is NOT true of human chromosomes?

(A) The haploid number is 23.
(B) Somatic cells contain 46 total chromosomes.
(C) There are 23 pairs of chromosomes.
(D) Gametes contain 2 of each of the 23 chromosomes.
(E) The diploid number is 46.

446. A mutation is most correctly defined as

(A) any change in the DNA sequence
(B) a detrimental change in phenotype
(C) any change from the wild type
(D) a change in DNA that has a lethal effect
(E) any change except that which has a neutral effect

447. To express an X-linked recessive trait, a

(A) male must be heterozygous for that trait
(B) female must be homozygous for that trait
(C) male must be homozygous for that trait
 (D) female must be heterozygous for that trait
(E) female must be hemizygous for that trait

448. A person with Tay-Sachs disease

(A) has a sex-linked condition
(B) has a mutation in a gene that controls lipid processing
(C) suffers from frequent bruising
(D) must limit the amount of meat in his or her diet
(E) is incapable of having male children

449. In genetics, a locus is

(A) a recessive gene
(B) a sex chromosome
(C) the location of an allele on a chromosome
(D) an unmatched allele on a sex chromosome
(E) a gene that produces a product that regulates another gene

450. If brown hair is dominant to black hair, then animals that are
homozygous dominant and animals that are heterozygous for this trait
have the same
(A) genotypes
(B) parents
(C) phenotypes
(D) alleles
(E) genetic sequences

451. Genes that are located on different chromosome pairs

(A) are sex-linked
(B) will appear together in gametes
(C) are not able to affect each other’s expression
(D) will sort independently
(E) are identified as being linked

452. A syndrome is a
 (A) genetic disorder
(B) group of signs and symptoms that tend to appear together
(C) series of fragile chromosomes
(D) disease that is undefined
(E) series of conditions that are rarely encountered

453. Which of the following is true about mitochondrial genetics?

(A) Human cells contain only maternal mitochondria.
(B) Mitochondria replicate and function independently from the
nucleus.
(C) Mitochondria have been found in some very large bacteria.
(D) The mitochondrial genome is invariant in humans.
(E) Mitochondrial genes more closely resemble eukaryotic than
prokaryotic genes.

454. If a person acquired a mutation that was detected in the DNA but did
not change any protein, then which of the following CANNOT be
true?
(A) The mutation was a silent mutation.
(B) The mutation occurred within an intron.
(C) The mutation was a neutral mutation.
(D) The mutation was a deletion mutation.
(E) The mutation was an inversion mutation.

455. A simple dominance monohybrid testcross with heterozygote will

result in a ratio of
(A) 1:3
(B) 1:2:1
(C) 1:2:2:1
(D) 1:1
(E) 9:3:3:1

456. If a daughter expresses a recessive gene that has a known simple

dominance, sex-linked inheritance pattern, then which of the following
 is true?
(A) She inherited the trait from her mother only.
(B) All of her sisters would also express the trait.
(C) She inherited the trait from her father only.
(D) All of her brothers and sisters would also express the trait.
(E) She inherited the trait from both parents.

457. Which of the following genetic conditions confers both an affliction

and an advantage to an individual?
(A) Colorblindness
(B) Blood group AB+
(C) Turner syndrome
(D) Sickle-cell anemia
(E) Down syndrome

458. Identify the result of incomplete dominance.

(A) A man with blood group O
(B) A person with medium-thick hair from a parent with thin hair and
a parent with thick hair
(C) A woman with blood group AB
(D) A person with long toes who has parents with short toes
(E) A person without hair who has two normal parents

459. What would be the most likely result if a person had a deletion
mutation in a gene that codes for a single tRNA?
(A) There would be no phenotypic changes because of wobble.
(B) All proteins would be affected but still effective.
(C) The mutation would not be lethal.
(D) There would most likely be significant changes in all proteins.
(E) The mutation would improve cell functions because it would be
more streamlined.

460. An individual with a genotype of AaBBCcDd would produce how

many different forms of gametes pertaining to these alleles?
 (A) 1
(B) 16
(C) 32
(D) 8
(E) 4

461. A centimorgan is a
(A) method to determine genetic defects
(B) measure of gene frequency
(C) measure of gene linkage
(D) method used to suppress some phenotypes
(E) measure of gene expression in rare events

462. Which of the following is the most probable expression of epistasis?

(A) When no male offspring are ever born to parents with a certain
phenotype
(B) When offspring with brown hair are afflicted with some condition
but those with black hair are healthy
(C) When all female offspring die at birth
(D) When parents with the same blood type have a child with another
blood type
(E) When an organism expresses more cellular receptors than normal

463. Which of the following is the best reference to the law of segregation?
(A) All chromosomes separate randomly during meiosis.
(B) Every gamete receives a random number of chromosomes.
(C) Gametes receive only one copy of each gene.
(D) Each gene separates from every other gene during meiosis.
(E) Chromatids migrate to opposite ends of the cell during mitosis.

464. If all males in a family are afflicted with a disorder such as hemophilia,
but females rarely are, then the inheritance pattern is likely to be
(A) codominance autosomal
(B) incomplete dominance X-linked
 (C) simple dominance recessive
(D) an expression of hypostasis
(E) X-linked recessive

465. In simple dominance, what would be the results ratio for the cross
AaBb × AaBb?
(A) 9:3:3:1
(B) 2:4:2
(C) 1:1:1:1
(D) 1:1
(E) 1:3:3:1

466. Which is the best way to express the relationship of mutagenesis to

carcinogenesis?
(A) The terms are equivalent.
(B) Carcinogenesis precedes mutagenesis.
(C) The terms are unrelated.
(D) Mutagenesis is always independent of carcinogenesis.
(E) Mutagenesis precedes carcinogenesis.

467. Given the following data, what do you conclude about the gene order?
Crossing mutants 1 and 2 produced 25 percent recombinants. Crossing
mutants 1 and 3 produced 3 percent recombinants. Crossing mutants 2
and 3 produced 20 percent recombinants.
(A) 2-1-3
(B) 1-2-3
(C) 1-3-2 and 2-1-3 are possible
(D) 1-3-2
(E) 1-2-3 and 2-1-3 are possible

468. What explains a normal curve representing the heights of individuals

in a population?
(A) Pleiotropy
(B) Epistasis
 (C) Hypostasis
(D) Polygenes
(E) Multiple alleles

469. Karyotyping is commonly performed to screen for what genetic

condition?
(A) Tay-Sachs
(B) Sickle-cell anemia
(C) Down syndrome
(D) Cystic fibrosis
(E) Hemolytic anemia

470. What do cells showing trisomy 21 and cancer cells have in common?
(A) Both are aneuploid.
(B) Both lead to death.
(C) Both indicate something treatable with gene therapy.
(D) Cells of both types will be detected and destroyed by killer T cells.
(E) Both are representative of every cell in the original body.

471. Transfusion of whole blood from Jim to Bill results in clotting and
death for Bill. But transfusion of whole blood from Bill to Jim
produces no crisis. Which is the best possible explanation?
(A) Jim’s blood has a much higher concentration of red blood cells
than Bill’s, and Bill cannot tolerate the difference.
(B) Bill has type O blood.
(C) Jim has type O blood.
(D) Jim is Rh+, while Bill is Rh−.
(E) Jim has had malaria.

472. If GGHH were crossed with gghh, what would be the most common
genotype of the F2 generation?
(A) GGhh
(B) GGHH
(C) ggHH
 (D) GGHh
(E) GgHh

473. When determining a karyotype, what chemical is added to the

collected cells to better observe the chromosomes?
(A) Acetone
(B) Colchicine
(C) Formaldehyde
(D) Crystal violet stain
(E) ATP

474. A phenotypic cure

(A) can prevent a disorder from being passed on to offspring
(B) can eliminate the defective gene in the parents
(C) can correct the defective expression
(D) can replace the defective gene in the offspring
(E) can suppress the defective gene in a carrier

475. During ovum formation in the ovary, nondisjunction of the X

chromosomes occurred and produced two ova genotypes. If these two
are fertilized normally, what are the possible resulting genotypes?
(A) XXY, Y0
(B) XYY, Y0
(C) XXY, XYY
(D) XXY, XX
(E) XX, YY

476. Which of the following cell collection methods is best associated with
fetal karyotyping?
(A) Cervical scraping
(B) Phlebotomy
(C) Buccal swabbing
(D) Amniocentesis
(E) Spinal tap
477. Any difference between the percentage of a population having a
defective gene and the percentage of the population expressing that
gene is
(A) called dominance
(B) expressed as epistasis
(C) identified as penetrance
(D) measured by application of the Hardy-Weinberg law
(E) called leakage

478. What is the cause of trisomy 21?

(A) Nondisjunction
(B) Exposure to carcinogens during the first trimester
(C) A fragile X chromosome
(D) Inheritance
(E) Infection with Toxoplasma gondii
 CHAPTER 15

Evolution

479. When males differ in appearance from females, this difference is

referred to as
(A) sexual dimorphism
(B) a primary sexual characteristic
(C) polymorphism
(D) hermaphrodism
(E) primary selection

480. Assume a small flock of birds is blown to a remote island where its
species has not been before. This is an example of
(A) the Hardy-Weinberg law
(B) the founder principle
(C) the bottleneck effect
(D) genetic drift
(E) disruptive selection

481. Which of the following taxonomic levels is the most inclusive?

(A) Genus
(B) Class
(C) Phylum
(D) Family
(E) Order

482. It is thought that the primitive atmosphere on earth prior to the

appearance of life contained all of the following gasses EXCEPT
(A) carbon dioxide
 (B) hydrogen sulfide
(C) sulfur dioxide
(D) nitrogen
(E) oxygen

483. The endosymbiotic theory

(A) can be observed in the symbiosis of fungi and algae in lichens
(B) is supported by human reliance on intestinal microflora for some
critical nutrients
(C) is observed in the interdependence of species in a biome
(D) posits that mitochondria and chloroplasts were once bacterial
symbionts of larger primitive cells
(E) is supported by the symbiosis observed between plants and
mycorhizzae

484. Speciation can follow the appearance of new alleles. These new alleles
arise by
(A) migration
(B) independent assortment
(C) errors in meiosis
(D) mutation
(E) random mating

485. Carbon 14 (14C) has a half-life of about 5,730 years. What does this
imply about using it for carbon dating?
(A) All 14C has fully decayed since its creation more than four billion
years ago.
(B) 14C can no longer be found in inorganic materials.
(C) To still be detectable, 14C must be regenerated continually.
(D) 14C can only be used for dating organic materials.
(E) 14C must be fixed by plants into organic form.

486. The theory of acquired inheritance

 (A) was replaced by the theory of evolution
(B) is supported by phenotypic data
(C) says that genes arise from mutations
(D) is supported by gene duplication mechanisms
(E) states that phylogeny is determined by evolution

487. The Miller-Urey experiment of 1952 showed that

(A) DNA could arise from inorganic synthesis
(B) amino acids, organic acids, and sugars could be formed
spontaneously under primitive atmospheric conditions
(C) DNA, and not DNA + proteins, was the storage molecule of
genetic information
(D) amino acids, nucleotides, lipids, and sugars could be formed
spontaneously under primitive atmospheric conditions
(E) primitive atmospheric conditions plus the presence of electrical
discharges could form lipid bilayers that are very similar to cellular
membranes

488. Which of the following is NOT an assumption made for the

determination of the Hardy-Weinberg equilibrium value?
(A) Natural selection does not occur.
(B) Mating is random.
(C) The population is finite and defined.
(D) There is no immigration and no emigration.
(E) Mutation does not occur.

489. Stabilizing selection occurs

(A) when the extremes of the population survive at higher rates than
the mean
(B) when the environment determines the survival of the population
(C) when one extreme of the population survives at a higher rate than
the other extreme
(D) when humans intervene and determine selection pressures
 (E) when the mean of the population survives at a higher rate than
either extreme

490. When a population develops into two reproductively isolated groups,

but this isolation is not based on geographic factors, then the process is
best identified as
(A) sympatric speciation
(B) random mating
(C) allopatric speciation
(D) adaptive radiation
(E) the founder effect

491. Which of the following is NOT true concerning organisms?

(A) They are in competition for resources with other members of their
own species.
(B) They have no need to respond to their natural environment.
(C) They differ individually in fitness.
(D) They fit best into a certain niche.
(E) They have genes in common with organisms not of their species.

492. Which of the following is thought to have occurred last in the

development of the first living cell?
(A) Abiotic formation of organic materials
(B) Formation of a lipid bilayer
(C) Formation of proteins
(D) Formation of RNA
(E) Formation of DNA

493. The concept of genetic drift

(A) involves the movement of genetic material through horizontal
transfer
(B) refers to random changes in the allelic distribution within the gene
pool
(C) involves the movement of genes across geographic distances
 (D) involves the movement of genes from one species to another
(E) involves the movement then isolation of a species

494. Which of the following are thought to have arisen the earliest?
(A) Giardia, which lack mitochondria
(B) Autotrophic eubacteria
(C) Coliphages
(D) Archaeobacteria
(E) Cyanobacteria

495. What is observed when two populations are completely isolated

reproductively?
(A) The onset of extinction
(B) Speciation
(C) Aneuploidy
(D) Hybridization
(E) Simultaneous geographic isolation

496. The formula (p2) + (2pq) + (q2) = 1

(A) expresses that both genotype and allele frequency remain constant
in a population
(B) demonstrates the process of speciation within a fixed environment
of a rapidly mutating population
(C) expresses the process of allopatric speciation
(D) expresses directional selection
(E) demonstrates disruptive selection within an invariant environment

497. Which of the following represents the correct sequence of geologic

periods progressing toward the current day?
(A) Cambrian → Triassic → Devonian → Tertiary
(B) Pennsylvanian → Triassic → Permian → Silurian
(C) Cambrian → Devonian → Cretaceous → Quaternary
(D) Triassic → Permian → Mississippian → Ordovician
(E) Jurassic → Triassic → Permian → Cretaceous
498. What distinguishes a predator from a parasite?
(A) Size
(B) Complexity
(C) Metabolism
(D) Habitation
(E) Hermaphroditism

499. Hybrid sterility is mostly caused by

(A) the inability of a hybrid to perform proper mating rituals
(B) the lack of fitness of the hybrid
(C) the inability of the hybrid to find its correct niche
(D) a lack of suitable mates
(E) mismatched chromosomes

500. The oldest fossil evidence for life dates to ___________________

years ago.
(A) about 540 million
(B) a little more than 5 billion
(C) about 13.7 billion
(D) about 3.5 billion
(E) about 270 million
 ANSWERS

Chapter 1: Enzymes and Metabolism

1. (A) In a eukaryote, the electron transport system resides in the
mitochondrion. There, the high-energy electrons harvested from glucose are
bled of their energy to drive the proton pumps. Bacteria are capable of
oxidative phosphorylation but are prokaryotic in structure, and their
electron transport system resides within their cell membrane, not within an
organelle.

2. (C) Halophilic means salt-loving, thus preferring salt concentrations that

are generally much higher than the physiological value of 0.85 percent.
These organisms may live in acidic or basic conditions, or they may prefer
either colder or warmer temperatures, so the only conclusion that can be
drawn from the information presented is relevant to salt levels.

3. (A) One acetyl CoA (with two carbon atoms) from glycolysis will attach
to a recycling molecule of oxaloacetate (four carbons) to produce a
molecule of citrate (six carbons). The cycle continues with a molecule of
CO2 being released, producing a molecule of α-ketoglutarate (five carbons),
which in turn releases another molecule of CO2 to produce succinyl CoA
(four carbons).

4. (D) Metabolic processes include anabolic, or synthetic, reactions where

smaller molecules are enlarged or extended with the storage of energy. The
opposite process, in which larger molecules are broken down into smaller
ones and release energy, is known as a catabolic reaction. The breakdown of
glucose to two molecules of pyruvate is therefore catabolic.

5. (B) One molecule of acetyl CoA entering the TCA cycle results in the
production of three molecules of NADH+ and one of FADH2. Each of these
carries one high-energy electron to the electron transport chain, which is
ultimately discarded onto an atom of oxygen to act as the terminal electron
acceptor and results in the production of H2O.

6. (B) The allosteric site of an enzyme is generally involved in regulation of

enzyme activity. A prosthetic group is any portion of the molecular
structure that may have substitution variability. A reactive group indicates a
component that is fed into the reaction itself and changes in structure. A
dehydration site is one located on a reactant, not on an enzyme.

7. (C) Paired carbon molecules removed from fatty acids are eventually fed
into the TCA cycle, and this results in the production of ATP from oxidative
phosphorylation. This process of removal is known as β-oxidation.

8. (D) While answer C might appear correct, the substrate level does not
change significantly as the food leaves the stomach and enters the
duodenum. What does change, however, is the pH of the food as it changes
location. While in the stomach, food is subject to a pH of between 1 and 2.
When it enters the small intestine, it is rapidly neutralized by bile and other
digestive components coming through the bile and pancreatic ducts.

9. (A) The word glycolytic refers to the breakdown of glucose or

carbohydrates. While this does release energy, the question asks for a much
broader term with the word any. Metabolic refers to reactions that both
synthesize and degrade, so answer B can be eliminated. Catabolic reactions
break apart large molecules into smaller ones, thereby releasing the energy
stored with their bonds.

10. (D) The TCA cycle defines a process whereby a molecule of acetyl
CoA is fed into a looping series of reactions that consumes the molecule
and restores the cycle for the input of the next one. For every two carbon
atoms contained within the acetyl CoA input, two molecules of CO2, one
molecule of ATP produced by substrate-level phosphorylation, three
molecules of NADH, and one molecule of FADH2 are kicked out.

11. (B) Three conditions define oxidation: (1) when a molecule gains an
oxygen atom, (2) when a molecule loses an electron, or (3) when a
molecule loses a hydrogen ion (proton). Oxidation is always coupled with
reduction; that is, when one molecule is oxidized, another is reduced.
Reduction is simply the opposite of oxidation. The conversion of NADH to
NAD indicates the loss of a hydrogen ion, thus oxidation.

12. (C) The maintenance of homeostasis requires the localized focusing of

energy to maintain order. Cells must constantly consume energy to offset
the loss of energy and organization due to the second law of
thermodynamics.

13. (A) ATP (answer D) commonly participates in reactions that are

catalyzed but is consumed in those reactions, so it is not catalytic. While
iron (answer B) is associated with catalysis, it is always as a component of
an enzyme. The suffix -ase (as seen in answer A) indicates an enzyme,
which is a large, globular protein with catalytic properties.

14. (E) Answer A describes a component that may act as an inhibitor, but
without further detail, it is too broad a term here and should not be
considered. Answers B and C both describe components that turn an
enzyme on. Answer D is a term used to describe a negative control on gene
expression. That leaves answer E as the correct choice. Materials that bind
irreversibly at an enzyme’s active site are considered enzymatic poisons.

15. (D) Energy is constantly required by any living organism, because it

must be used to counter the degenerative effects of increased randomness,
thus answer A is true. Energy is also required to “do work” that allows all
cellular functions to continue, so answer B is equally true. Lastly, since
making a specific alteration in a cell is also “doing work,” answer C is also
true, eliminating answer E. Thus, answer D is the correct answer.

16. (D) Glycolysis refers to the catalysis of glucose to pyruvate through one
primary cellular route. It takes five enzymatic steps to reduce glucose to
two molecules of phosphoglyceraldehyde and five additional steps to
rearrange these two molecules to the structure called pyruvate. Thus,
glycolysis involves 10 steps, making answer D correct.

17. (C) Photosynthesis actually gives off oxygen as a toxic waste gas. The
process takes inorganic carbon from the air in the form of CO2 and, with
H2O broken down by photolysis, uses these raw materials to produce
glucose (C6H12O6) and the waste gas O2.
18. (B) Some inhibitors bind enzymes at sites other than the active site, but
these are identified as allosteric inhibitors. A poison is an inhibitor that
irreversibly binds and permanently deactivates an enzyme. While answer B
does not describe what a competitive inhibitor does, the fact remains that it
cannot be processed at the active site, making this choice the correct one.

19. (A) When a high-energy electron is delivered to the electron transport

system from NADH, it starts traveling down the chain at the flavoprotein
FMN. Some energy from this electron is then used to pump a pair of
hydrogen ions (H+) from the matrix to the inner membrane space. The
electron is then transferred to the second component, coenzyme Q, which
repeats the same function. Thus, this latter component transfers both
electrons and protons.

20. (E) Bacteria normally do not reproduce or metabolize faster at higher

body temperatures. Fever does not block bacterial protein synthesis,
otherwise it would always be effective in halting bacterial growth. Answer
E is correct, because an elevated body temperature causes all bacterial
enzymes to function at less than the optimal rate, thus reducing the growth
rate of the bacteria and giving the body a better chance to clear the
infection.

21. (E) Anaerobic respiration is defined as an ATP-generating process in

which molecules are oxidized and the final electron acceptor is an inorganic
molecule other than oxygen. Oxygen can act as a final electron acceptor
like the other answers, but when it is used for that purpose, it is known as
aerobic—not anaerobic—respiration.

22. (B) This question is related to the previous one. The basis for
identifying the form of respiration is always based on the substance that
acts as the final electron acceptor of the process. If the final electron
acceptor is oxygen or an inorganic ion, it is considered aerobic or anaerobic
respiration, respectively. If the final electron acceptor is an organic
molecule, the process is fermentation.

23. (E) Cofactors are normally separate molecules from the enzyme. While
the additional molecular size would affect the enzyme, it would not
permanently disable it, because as soon as the modified substrate was
removed from the reaction, the enzyme could act on the unmodified
substrate.

24. (C) Lipids (oils or fats) contain 9 calories per gram (C/g), while proteins
and carbohydrates both contain 4 C/g. Thus, if 6.5 g of protein is consumed,
there are 6.5 g × 4 C/g, which equals 26 C available for use by the body.

Chapter 2: DNA and Protein Synthesis

25. (E) Deoxyribonucleic acid (DNA) is a polymer of nucleosides. Each
nucleoside is composed of a nitrogenous base coupled to a pentose sugar. If
the sugar is ribose, the resulting polymer is RNA; if it contains deoxyribose,
it is DNA. All sugars contain carbon, hydrogen, and oxygen. Thus, all DNA
contains these and the nitrogen of the nucleoside. The only element listed
that is not included here is iron.

26. (B) Restriction endonucleases cut through both strands of DNA but
usually at very specific sequences. Most of these sequences are
palindromes. Thus, the complementary sequence for answer A, AGCT
would read (in the opposite direction) AGCT, making this palindromic. The
same is true for answers C, D, and E. However, it is not true for answer B,
where GACGAC would read in a similar manner GTCGTC.

27. (C) One of the peculiarities of most restriction enzymes is that they do
not cut straight through; rather, they make a jagged cut a base or two apart
on the two strands in the same locations within the palindromic sequence.
This produces an overhang of single-stranded bases. These overhangs are
called sticky ends, because they will spontaneously reanneal with any DNA
cut with the same restriction enzyme.

28. (D) Replication of both eukaryotic and prokaryotic DNA begins the
origins of replication (ORI). This melting is normally accomplished by
enzymes, such as helicases, that separate the two complementary strands.
Enzymes that prevent supercoiling are called topoisomerases. Sigma (σ)
factors identify where a polymerase binds to DNA. Ligation is
accomplished by DNA ligase.
29. (A) If the DNA triplet AAC were transcribed, the corresponding
complementary sequence on the mRNA would be UUG. The UUG
sequence represents the codon that would be used within the ribosome.
Looking at the table providing the genetic code, it can be determined that
UUG codes for Leu. The correct answer is therefore leu(cine).

30. (C) Answer A is incorrect, because sometimes the change will produce
an effect even when in this location. Answer B is incorrect, because even if
there is a change in the amino acid inserted, it may or may not produce a
dysfunctional protein that may have a lethal effect. A change in any amino
acids may affect protein function regardless of where it is located. Answer
E is incorrect because such a mutation only infrequently has a lethal effect.

31. (D) The polymerase chain reaction (PCR) is a method that uses thermal
cycling to amplify the number of copies of specific DNA sequences. The
process requires specific paired oligonucleotide primers that are unique for
the sequence desired, dNTP monomers, a buffer complex commonly
referred to as the master mix, Mg2+ ions, and the enzyme DNA polymerase.

32. (B) In biology, the central dogma refers to the tenet that all life
processes originate as genetic templates stored as codes embedded in DNA
and copied during DNA replication. These codes are then converted into
their equivalent RNA form in the process of transcription and finally
translated into protein products within the ribosomes. This sequence of
materials is unidirectional from DNA to RNA to proteins.

33. (A) An open reading frame (ORF) refers to a long sequence of RNA
that, when translated, produces a protein. That means it starts with the
codon AUG and ends with any one of the three STOP codons. However, the
start of the ORF can be identified by its complementary sequence in DNA,
or the triplet TAC.

34. (E) The intact prokaryotic ribosome is identified as being 70S and
composed of a large (50S) and small (30S) subunits. The equivalents for the
eukaryotic ribosome are 80S (intact), 60S (large subunit), and 40S (small
subunit). The numbers are not additive because they measure density, not
mass.
35. (C) A silent mutation means that the resulting protein is identical in
function to the original version, or wild type. Also of little consequence are
mutations found within most noncoding regions. However, any mutation
that changes a highly conserved sequence would nullify its purpose. Thus,
if such a mutation occurred within the TATAAT box of a critical enzyme,
that gene could no longer be expressed and the cell would likely die.

36. (E) DNA ligase is an enzyme associated with DNA replication, not
degradation, so answer B can be excluded from consideration. The enzymes
identified in answers C and D are also polymerases associated with
synthesis, so they can be ignored. β-lactamase (answer A) is an enzyme best
associated with the ability of bacteria to resist the effects of certain
antibiotics, not viruses. Thus, only answer E remains.

37. (B) The initiation of bacterial transcription is controlled by recognition

proteins identified as sigma factors. These factors serve to select the genes
that should be expressed under those same conditions for optimal cellular
function. If the conditions in which the cell lives changes dramatically,
different sigma factors will be expressed, which then allows for the rapid
shift in metabolism that is required for the cell to survive.

38. (D) RNA transcription takes place only where DNA might be present,
which includes the nuclear region of bacteria or its eukaryotic equivalent of
the nucleus. However, both mitochondria and chloroplasts—once thought to
be bacterial symbiotes of a primeval host cell—are also capable of
transcribing and expressing their own genes using their own genetic code.

39. (C) Among evidence for the endosymbiotic theory are the facts that
chloroplasts and mitochondria have their own separate genome, bacteria-
like DNA polymerases, and bacterial-like ribosomes. The ribosomes of the
eukaryotic cell are found only within the cytoplasm, although they are
commonly closely associated near the endoplasmic reticulum.

40. (D) Base pairing is most commonly associated with the double-stranded
structure of DNA. However, RNA is also capable of base pairing with itself
to form regions of double-strandedness, so answer A is incorrect. DNA is
found within bacteria, mitochondria, and chloroplasts, so answer E can be
ignored. Answer B reverses the correct association, so it is also wrong.
Answer C is actually true for both DNA and RNA, so only answer D
remains.

41. (A) Helicase is first involved in the separation of the two strands of
DNA. Topoisomerases are involved in preventing supercoiling. DNA
polymerase is responsible for the actual manufacture of the new strand after
reading the base sequence on the template strand. DNA ligase is involved
later for rejoining separate Okazaki fragments in lagging-strand synthesis.
Endonuclease is the only enzyme not required.

42. (A) Ribosomes are clusters of several strands of rRNA intertwining

through ribosomal proteins. Answer C is one aspect included in answer E,
and both are associated with mRNA in eukaryotes. Answer D involves
converting nucleotide sequences from RNA to a DNA form. Answer B
identifies processes involving protein modifications following translation.

43. (E) Eukaryotic DNA contains extensive noncoding regions interspersed

between those that contain codes used for the production of proteins.
Following transcription, the newly manufactured RNA is processed by
splicesomes to remove these introns and rejoin the essential coding regions.
This shortened strand is then further modified at both the 3′ and 5′ ends
before being released from the nucleus for translation in the cytosol.

44. (B) The concept of wobble involves the third position of the codon. This
position is the one that permits the greatest latitude in changes without
necessarily changing the resulting amino acid to be inserted during
translation and is thus most likely not to change the essential nature of the
resulting protein. Only answer B reflects a single change in the codon at
this third position.

45. (B) During the first phase of initiation, the ribosome engages mRNA.
The second phase—elongation—lasts the longest, as each tRNA brings its
appropriate amino acid into the ribosome for addition to the elongating
protein. During the final phase, termination, a stop codon is encountered
and the ribosome disassociates.

46. (C) Hybridization between two strands of nucleic acid is highly

dependent on the proper orientation of the various bases to each other, and
G · C combinations contain three hydrogen bonds, while A · T pairs contain
only two. Although the sequences found in both answers C and E would
hybridize under certain conditions, answer E has several mismatches that
would reduce the binding strength.

47. (A) The photons within ultraviolet (UV) wavelengths contain

appreciably more energy than those of visible light. Depending on that
energy level, UV light will either cause the production of thymine dimers or
nick and degrade the DNA. Degraded DNA will, if not repairable, induce
the cell to undergo apoptosis and die.

48. (C) DNA is DNA, regardless of what organism or virus is its source.
That means that it is of uniform dimensions throughout its length. DNA is
composed of deoxyribose and contains thymine, whereas RNA is composed
of ribose and contains uracil. Both groups of organisms share the same
genetic code, although it is slightly different in mitochondria and
chloroplasts.

49. (A) The Shine-Dalgarno sequence is a sequence of bases found within

the noncoding leader section of mRNA. This sequence is vital during the
initiation phase of translation, as it provides the recognition signal used by
the ribosome to orient the mRNA properly with the rRNA of the ribosome.
It ensures that the start codon will be in the proper position to initiate the
translation process.

50. (D) The self-cleaving ability of some RNAs, known as ribozymes,

provides evidence of biologic catalysts in a nonprotein form existing prior
to the development of proteins.

51. (E) mRNAs are exported out of the nucleus for translation within the
cytoplasm. These proteins are then escorted back into the nucleus, where
they begin to associate with strands of rRNA transcribed from DNA regions
within the nucleolus. These subassemblies are then exported back out into
the cytosol for final assembly as ribosomes to participate in translation.

52. (E) Fidelity means accuracy in the copying or reproduction process, and
more than 50 genes are associated with DNA replication and DNA repair to
ensure accuracy. DNA polymerase makes mutational mistakes about every
1,000 bases, but it has an exonuclease proofreading function that allows it
to correct the error. This improves its fidelity by another three orders of
magnitude.

53. (E) A nonsense mutation is defined as a change in the DNA that results
in the appearance of a stop codon in the resulting mRNA where it
previously did not exist. This almost always produces a change in
phenotype, as the resulting protein is either severely debilitated or
nonfunctional. If this mutation affects a critical protein, then it will likely be
lethal. Since introns are removed from the mRNA prior to translation,
mutations within these regions have no cellular effects.

54. (B) The question describes a polyadenylation (polyA) sequence, such as

is seen at the 3′ end of mRNA exported from the nucleus for translation into
a protein. rDNA codes for both ribosomal proteins and rRNA and has no
such characteristics. cDNA is similar in structure to rDNA but lacks introns.
Polyadenylation is a normal part of posttranscriptional modifications, so the
polyA tail is not a waste product.

55. (D) While DNA ligase is used in genetic engineering to finalize the
construction of modified plasmids, it is also normally present in the
replisome, and both are active in the lagging-strand synthesis of DNA
replication. Restriction enzymes are universally used to cut apart DNA
containing genes of interest.

56. (D) Question 46 mentioned that G · C base pairings involve three

hydrogen bonds, whereas A · P base pairings involve only two. Answers B
and C can be eliminated because they do not form, as they are
noncomplementary. Answer A and its RNA equivalent in answer E indicate
that just two bonds are involved. This means that answer D is the correct
choice.

57. (A) Lagging-strand synthesis is much more involved than leading-

strand synthesis and requires the function of multiple enzymes in a
complicated sequence. DNA ligase is required to remove the nicks in one of
the DNA strands only following lagging-strand synthesis.
58. (C) The Pribnow box identifies a highly conserved sequence in
prokaryotes that is required for RNA polymerase to recognize and bind to
DNA in the promoter region to initiate transcription. This sequence, which
is found 10 base pairs prior to the start point of transcription is 5′-TATAAT-
3′. Its equivalent in eukaryotes, again indicating the binding site for DNA-
dependent RNA polymerase, is 5′-TATA-3′.

59. (B) Answer D describes a theoretical process called conservative

replication, which was hypothesized as a possible replication method before
the confirmation of the actual semiconservative mechanism described in
answer B. All other choices are nonexistent.

60. (E) Genes are generally identified by a three-letter code, usually printed
in italics, and refer to the function with which they are best associated. For
example, the genes associated with the bacterial manufacture of the amino
acid tryptophan are identified as trpE, trpD, trpC, trpB, and trpA. It is thus
easy to link recA to answer E, recombination repair.

61. (E) All three forms are capable of forming short regions of double
strandedness, are chemically identical, contain uracil in lieu of thymine, are
exported out of the nucleus, and are present within the ribosome during
protein synthesis. The one thing that distinguishes mRNA from the other
two forms is that mRNA contains the code necessary for the production of
proteins, whereas this is not true for rRNA and tRNA.

62. (A) While salts can be used to inhibit hydrogen bonding between DNA
strands, once added it would continue to do so, preventing amplification in
any additional steps. DNA polymerase does not melt the complementary
DNA strands; that function is accomplished by helicase within the cell.
Normal double-stranded DNA will melt at 95°C to 100°C, which is
accomplished during the heating phase of the PCR process.

63. (C) While DNA fragments could be separated by the techniques

presented in answers A, B, and D, these methods would be cumbersome
and inefficient. The technique presented in answer E does not exist. One of
the most commonly used methods used in the genetics laboratory is the
Southern blot. Before the DNA fragments can be identified or used for
cloning, the simplest separation method is agarose gel electrophoresis.
64. (B) Answers A, D, and E state or imply that this transfer is relatively
energy-independent. However, the formation of peptide bonds, which store
energy, requires the addition of sufficient energy to activate the linkage.
Answer C references catalytic action, but answer B specifically identifies
the energy expense, so it is the preferred answer.

Chapter 3: The Molecular Biology of Eukaryotes

65. (E) The production of RNA requires an RNA polymerase enzyme, so
answers A and C are incorrect. Answer D refers to an enzyme that degrades
rather than synthesizes RNA, so it can be excluded. Without knowing
which of the two remaining choices (answers B and E) is right, it would be
better to choose the one that was probably identified later in the discovery
process, meaning answer E.

66. (B) An intron is not a mobile genetic element. A DNA transposon is the
simplest of these elements in eukaryotes, but it has no similarity to viruses.
LINE and SINE refer to long (and short) interspersed elements,
respectively; they are also known as nonviral retrotransposons. This leaves
LTR (long terminal repeats) elements that contain retroviral genes as the
correct answer.

67. (C) The Human Genome Project made some astounding discoveries,
including the amount of human DNA that actually codes for human
components. When added up, all noncoding regions amount to more than
98 percent of the human genome, meaning that only about 2 percent
actually codes for “us.” Two percent of 1.8 meters is 3.6 cm, making
answer C the correct one.

68. (D) Telos in Greek refers to “the end, remoteness, or far away.” Meros,
also Greek, refers to “a part or portion.” Thus, telomere means “parts on the
ends.” Telomeres are the terminal repeated sequences found on the ends of
chromosomes that are associated with stabilizing the ends.

69. (C) The replisome is a cluster of proteins, enzymes, and assorted

cofactors that are congregated in the nucleus after being manufactured
during the G1 phase of the cell cycle. Their function is to replicate the entire
DNA genome prior to cellular division. This machinery is not associated
with RNA at all. It also has nothing to do with protein synthesis.

70. (E) The term genotype refers to the genetic content of an organism. This
genetic content is expressed as a physical manifestation in the phenotype.
All mutations change the genotype but do not necessarily change the
phenotype. A back mutation is defined as a change in the DNA that returns
a previously experienced forward mutation back to its original version, or
wild type.

71. (D) Heterogenous nuclear RNA (hnRNA) is the initial, maximum-sized

nucleic acid transcript transcribed within the nucleus, where the introns are
removed and the exons are spliced together. Afterward, a 7-
methylguanosine cap is placed on the 5′ end of the transcript and a polyA
tail is added to the 3′ end. The cap described by answer D is observed on
bacterial mRNA and is not a posttranscriptional modification.

72. (A) Eukaryotes are capable of fine-tuning gene expression levels with
multiple activator-and suppressor-binding regions in trans to the gene they
regulate. Thus, they are capable of transcribing low, moderate, or high
levels of mRNA—and many variations in between—based on the number
and type of transcription factors bound at their appropriate binding sites.

73. (A) Protein hormones bind to very specific receptor molecules

expressed on the surface of cells. Once bound, they produce a second
messenger, such as cAMP, that greatly amplifies the signal. Steroid
hormones ignore surface receptors and pass freely through the cell
membrane. Once in the cytosol, they bind to cytosolic receptors.

74. (B) The σ70 subunit is used to identify where RNA polymerase core
enzyme components (2α + β + β′) will bind to DNA just prior to
transcription, but these are found only in prokaryotes. The eukaryotic RNA-
P core enzyme components are not associated with the initial recognition of
the binding site. Both transcription factor IID (TFIID) and a supporting σ
factor are required for accurate recognition.

75. (E) Any enzyme that synthesizes DNA would be identified as a DNA
polymerase. No enzyme is capable of synthesizing proteins. Nucleic acid
polymerases work by synthesizing a strand that is complementary to the
template, and this complementarity requires an anti-parallel molecular
orientation.

76. (A) Oncogenesis is the formation of a cancer. An oncogene is usually a

gene that once was associated with growth regulation of a cell but mutated
into a form that could no longer fulfill that function. The term proto-
oncogene is used to describe any growth regulatory gene that has the
potential to be mutated into an oncogene.

77. (C) Spacer DNA accounts for about 24 percent of the human genome
and is noncoding. Thus, even a large deletion mutation would have no
effect on gene expression or control. An inversion mutation would have no
effect on any gene expression.

78. (B) Helicase is responsible for melting the DNA helix by breaking the
stabilizing bonds between the two complementary strands. SSB stands for
single-stranded binding proteins, which are responsible for preventing the
two separated strands from reannealing before replication by the DNA
polymerase.

79. (B) Denaturation of histones would most likely destroy a cell by

preventing it from controlling many vital cellular processes. DNA
methylation is a recognized epigenetic mechanism that results in the
downregulation of gene expression.

80. (B) The Wnt pathway has a significant role in controlling cell growth,
but loss of this control resulting in a cancer is associated with mutations.
HPV does interfere with p53, but in doing so, it prevents rather than causes
cell death. There are more than 50 DNA repair mechanisms, none of which
are affected by viral expression. The viral capsid protein identified as L1
commonly is not even expressed in cells transformed into cancers by HPV.

81. (D) A bacterial repressor is a protein that acts as a DNA binding protein
that attaches to a specific DNA sequence found only within the operator
region of a bacterial operon and prevents transcription. Eukaryotic control
is exercised by regulatory proteins binding to DNA at the periphery (in
trans) of the gene controlled.
82. (B) The lowest level of organizing eukaryotic DNA is when about 200
base pairs are wound around eight molecules of histones into a 10-nm
structure known as a nucleosome. Successive nucleosomes are then
organized into a 30-nm structure known as a chromatin fiber. Sections of
chromatin fiber reach maximum compaction in the form of the highly
condensed chromosome.

83. (C) The mRNA produced by eukaryotic cells contains the code from
only one gene and is always monocistronic. Cells are capable of producing
two versions of a final mRNA, usually one longer version that results in a
membrane-bound protein and an alternately spliced, shorter version that
will be secreted from the cell.

84. (D) Histones are proteins that contain no repeating nucleic acid
sequences. Nucleosomes are regions of organized DNA of any sequence
structure. Simple repetitive nucleic acid sequences are found in telomeres
on the ends of chromosomes, in microsatellites found throughout the
genome, and within the centrosome regions as well.

85. (B) mRNA produced by bacteria is of a simpler structure than that of

eukaryotes. Both eukaryotic and prokaryotic mRNAs have a nontranslated
leader sequence at the 5′ end that is shorter in the prokaryotic version.
Bacteria have a short region where the molecule flips back on itself,
forming a hairpin loop and demonstrating double-strandedness because of
the complementary regions, and this resides at the 3′ end of the molecule.
Answers A, C, and D are all located on the 5′ end and can be excluded.
Answer E has no relevance here.

86. (C) No enzymes rejoin introns or terminate translation. Rejoining exons

is not the function of a ribozyme. Any RNA that affects transcription is
called RNAi, or interfering RNA, and not a ribosome. A ribozyme is an
autocleaving segment of RNA.

87. (D) Researchers in the 1970s first found the “beads-on-a-string” pattern
associated with DNA packaging after digestion with solvents. Further
analysis discovered that there were four pairs of histones (two each of H2A,
H2B, H3, and H4) that served as a core or spool around which 146
nucleotide base pairs were wound. These nucleosomes are connected
together in series by an additional 50 base pairs of linker DNA each.

88. (A) The best way to follow gene expression is to extract the mRNA
resulting from transcription at regular time intervals. A Northern blot can be
used to identify specific sequences following electrophoresis and so might
be considered correct, but a microarray permits much more rapid
throughput and simpler analysis.

89. (D) The Shine-Dalgarno sequence is essential for mRNA to orient

correctly alongside the 16S rRNA in the ribosome prior to translation. It is
found within the nontranslated leader sequence of mRNA. This eliminates
answers A, B, and C from consideration as they all refer to DNA, not RNA.
Thus, answer D can be confirmed by elimination even if the function of the
sequence is not known.

Chapter 4: Microbiology
90. (D) The cell wall of bacteria is composed of peptidoglycan constructed
from a polymer of n-acetylglutamic acid and n-acetylmuramic acid, while
that of fungi is composed of chitin. Bacteria contain the 70S bacterial
ribosome, whereas fungi have the 80S eukaryotic ribosome. Bacteria lack
the organelles that all eukaryotes, including fungi, contain. The bacterial
genome is circular, but fungi have linear chromosomes.

91. (B) Microscopes are used to confirm diagnosis of the species of

tapeworm, but this diagnostic is based on a recovered proglottid.
Serological methods are available but are inadequately sensitive for routine
diagnostic use. The most useful diagnostic method is the observation and
identification of ova passed in the stool of infected individuals.

92. (E) While bacteria are certainly capable of using dead organic material
as a food source, there still has to be some other organismal source to bring
the organic material left behind into being. Detritus is consumed by other
organisms long before it can get that far down in the sea. The first life on
the scene are lithotrophic bacteria.
93. (C) All viral coats are composed of protein. Not all viruses have lipid-
based envelopes surrounding their capsids. Transcription enzymes are not
required by most DNA viruses. The bare essential structures possessed by
all viruses are a protein-based capsid and a genome of either RNA or DNA.
Many viruses have components beyond this minimum, but all have these
two.

94. (D) Antibiotics demonstrate selective toxicity, damaging bacterial

structures or interfering with bacterial functions more than with those of
humans. The membrane differences between prokaryotes and eukaryotes
are small and make safe targeting by antibiotics difficult, although a few do
exist.

95. (A) Bacterial ribosomes are smaller in terms of both the size of their
rRNAs and in the number and disposition of proteins within their subunits.
This is reflected in their sedimentation coefficient, which is a measure of
their density in a solution. Their proteins are smaller and fewer in number,
and their rRNA composition is also less. Both prokaryotic and eukaryotic
ribosomes have identical functions.

96. (E) The bacterial genome is circular, double-stranded DNA. The

mitochondrial genome is nearly identical but smaller in size.

97. (B) The only accurate comparison between a bacterial coccus and a
polyhedral virus is their general, roughly spherical shape.

98. (A) The flagellum is composed of three basic parts: the basal body, the
hook, and the axial filament comprising repeating flagellin subunits. The
basal body rests on the surface of the cell membrane, and the hook extends
through the cell wall.

99. (C) Chitin is the polysaccharide used by fungi to construct their cell
wall. Cellulose is the cell wall material used by plants, not bacteria. Lactose
is a disaccharide and not used as a cell wall component in any organism.
Chromatin is a descriptive term used to describe eukaryotic DNA, not the
bacterial genome. Actin is similarly not associated with the cell wall. Fungi
use chitin to build their cell walls, and bacteria use peptidoglycan.
100. (C) Seven genera of bacteria can form endospores. These are most
analogous to lifeboats formed and released in hostile environments to
permit the organism to survive in a highly condensed and nonmetabolizing
form.

101. (B) Bacteria are much simpler in form and function than eukaryotes.
Because of their genomic size, eukaryotic cells must separate their ability to
grow and metabolize from their ability to divide into separate phases of a
cell cycle. Bacteria, on the other hand, are capable of simultaneous DNA
replication, transcription, translation, and cellular division by binary fission.

102. (B) Viruses are organized into the seven classes of the Baltimore
system. Class I includes the double-stranded DNA viruses variola, which
causes smallpox; herpes viruses; adenoviruses; and the T-even
bacteriophages.

103. (D) Rickettsia are bacteria and thus possess all the characteristics that
define those organisms. Along with chlamydia, they comprise two bacterial
groups that are obligate intracellular parasites, like all viruses.

104. (E) The word dimorphic is Greek for “two forms.” Answer A
describes two mechanisms, not forms, and so is incorrect. Although answer
B is correct in describing fungi, the word form is not used to describe
genetic content, so it is out as well. All fungi have a cell wall, so answer C
is also not the correct choice. Answer D is true about fungi, but again it
describes mechanisms, not forms.

105. (A) A back mutation restores the wild type. A second mutation that
restores the original phenotype is called a suppressor mutation. A frameshift
mutation describes any mutation that adds or subtracts a base (or bases)
within the mRNA that drastically changes the coding for the amino acids
downstream from the change. A conditional mutation only can be observed
under certain environmental parameters.

106. (A) Antibiotics usually work against bacteria by targeting some

structure or mechanism that is distinctive within those cells. INH works
against only a certain class of bacteria whose cell walls are composed
partially of waxy mycolic acids. Only one of the three bacteria listed are
within this group, the genus Mycobacterium, species of which cause
tuberculosis and leprosy.

107. (A) A transposon is a mobile genetic element that codes only for its
own reproduction. Restriction endonucleases are identified by the first letter
of the genus and the first two letters of the species, such as EcoRI (from
Escherichia coli). The small letter p is commonly used to designate a
plasmid, so answer A is correct.

108. (D) Replica plating involves growing suspected mutant-containing

colonies on nutritionally complete media. A sterile piece of cloth is then
used to transfer some of the colonies onto media that usually lacks some
key substrate or growth factor. Nutritionally deficient mutants can therefore
be identified as those colonies that can grow on the original plate but are
missing on the replicas that lacked the key component.

109. (C) Plasmids are small, circular, double-stranded DNA components

that are self-replicating. They usually contain a number of genes that can be
expressed in the bacterial cells in which they are found and are normally
classified based on this transferrable function.

110. (E) cDNA is normally produced by using mRNA, after the noncoding
introns have been removed, as a template that an RNA-dependent DNA
polymerase (or reverse transcriptase) can use to transcribe into DNA. The
difference between the original DNA used to produce the mRNA and the
engineered cDNA is that the latter contains only the coding segments of the
original.

111. (B) An autoradiograph is produced when some radioactive material,

usually attached to a probe, is placed next to photographic or radiographic
film. After an appropriate exposure time, the film is developed, and the
researcher can visualize where the specific target is located in the original
material.

112. (D) Viroids are segments of naked single-stranded RNA transferable

between plants by arthropods that produce diseases in their hosts. They are
not viruses, because they lack envelopes and capsids. Multipartite viruses
are unique to plants and have multiple genomes packaged into separate
capsids.

113. (C) Cytoplasmic streaming involves the continual growth and

expansion of the cytosol of a cell as it expands outward. Mycoplasmas are
bacteria without cell walls that lack this capability. Cellular slime molds are
single-celled and amoeboid in movement. Acellular slime molds form large
multinucleate cell masses as they expand by cytoplasmic streaming along a
forest floor, consuming leaf debris and other detritus.

114. (E) Paragonimus westermani, or lung fluke, has a complex life cycle.
The primary host in which the sexual stages form sheds eggs in its feces,
which hatch in water. Then the organism changes form several times, using
first a snail and then a crustacean such as a crawfish as secondary hosts.
The organism completes its life cycle when the primary host eats infected
undercooked crustaceans.

115. (E) Bacteria that can survive in both oxygen-rich and oxygen-deficient
conditions are called facultative anaerobes. None of the most common
gasses in the atmosphere, including water vapor, oxygen, carbon dioxide,
and nitrogen are toxic to these anaerobes. Only chlorine, a halogen toxic to
all life forms due to its denaturing effect on proteins, would be hazardous to
facultative anaerobes.

116. (A) Warts are the result of uncontrolled cell growth. The infectious
agent that causes them is spread by contact. Human genital warts are caused
by infection of epithelial tissues with HPV, primarily of genotypes 6/11,
which is why the new HPV vaccine immunizes against these normally non–
cancer-causing strains.

117. (C) Consuming a material as a sole carbon source simply means that
the bacterium can survive if fed no organic material other than DNA, and
carbon and electrons could be derived from this source energy. Because
many bacteria can degrade DNA, this one is not the threat it may seem. In
essence, it is no big deal.

118. (B) Transformation is the process of moving naked DNA from cell to
cell. It was shown in classic experiments in the late 1920s that DNA from
dead bacterial cells could be incorporated into living cells, transforming
them from nonpathogenic to pathogenic forms in mice.

119. (D) Most fungi are capable of both sexual and asexual reproduction. In
many cases, asexual spore forms are morphologically similar to the sexual
spore forms, but only the latter are used for proper taxonomic identification.
The ascomycetes are identified by the presence of an even number of
sexually produced spores within small sacs usually totaling four or eight in
number.

120. (C) Boiling the bag would denature all of the vital proteins. The
addition of gluteraldehyde is bad, because it is very toxic. The alcohol
would be ineffective against a fungus at that concentration. Ultraviolet light
would be ineffective for that volume and packaging. The best solution
would be to filter sterilize the unit, as the organism is a pathogenic yeast
with a cell size about 10 times the filter pore size given.

121. (A) The term generation time means the amount of time required for a
bacterial culture in log phase to double in number—that is, the time
necessary for every cell to divide once (t). Knowing this, if there are 10
cells at t = 0 min, then there would be 20 at t = 20 min, 40 at t = 40 min, 80
at t = 60 min, and so on. Continuing the count brings you to a total of 5,012
at t = 180 min.

122. (B) Ringworm produces a roughly circular pattern of inflamed, itchy

skin that expands gradually over a period of days to weeks. It is caused by a
type of fungus called a dermatophyte and is closely related to similar
organisms that cause jock itch and athlete’s foot.

123. (D) When bacteria are first introduced into fresh culture medium, they
pass through lag, log, and stationary phases. When final depletion of
nutrients is completed, the culture starts to die off, and the number of viable
cells steadily drops as the culture passes through a logarithmic decline
phase on its way to extinction.

124. (E) The techniques used to stain bacterial cells in order to visualize
them under a light microscope are as old as the science of microbiology
itself. The Gram stain is universal, as it differentiates thick-walled, Gram-
positive cells from thin-walled, Gram-negative cells.

125. (A) The cell walls of bacteria and fungi are of different materials, with
peptidoglycan used by bacteria and chitin by fungi. The bacterial genome is
organized as a single circular, double-stranded DNA loop, whereas a fungal
genome is packaged as linear chromosomes within a nucleus. Bacterial
ribosomes are identified as 70S, but eukaryotic ribosomes are 80S. Bacteria
are not diploid and thus cannot reproduce with sexual mechanisms, whereas
fungi, in the filamentous form, can.

126. (C) For a virus to replicate, it must first attach to a host cell,
eliminating all answers but A and C. Once attached, the virus either forces
the cell to bring the virus into the cytosol by endocytosis, or it introduces its
genome by injection. This eliminates A and makes C the correct choice.

127. (B) The reason the bubbles form with some bacteria is because they
have the enzyme peroxidase, which catalyzes the reaction that converts
H2O2 into water and the much less toxic oxygen gas O2 (thus the bubbles).
Because this organism can detoxify oxygen, it can grow under aerobic
conditions.

128. (D) Inhalation anthrax occurs when a person inhales anthrax

endospores from some source. These change from endospores to vegetative
cells under the conditions found in the lungs and rapidly grow and produce
numerous toxins that characterize this fatal infection. The only way this
person could be helped is to begin an immediate regimen of appropriate
antibiotics.

129. (D) Ambisense viral genomes encode their proteins in two different
directions, and although these genes may overlap, the host cell ribosome
can read the mRNA in only one direction. The reverse sequence code must
be transcribed into a complementary strand that is read in the same
molecular direction: 3′ to 5′.

130. (C) No matter how they are disguised, circular, double-stranded DNA
and 70S ribosomes indicate a bacterial cell. Answer C is correct, in spite of
the lack of cell wall, because of two possibilities: the organism may be a
mycoplasma or a penicillin-induced L-form.

131. (B) By most definitions, a virus is considered nonliving, although

admittedly, our definition of life is deliberately constructed to exclude
viruses. The only statement that is not true of viruses is that they have a
membrane. Many lack a lipid envelope, and their exterior surface is
composed entirely of protein.

132. (E) A prion is a protein produced by a mutated PrP gene that is highly
resistant to degradation and has the ability to convert the normal protein
form into a mutant configuration. If a person (or animal) ingests this prion,
it slowly accumulates in the nervous system and produces a spongiform
encephalopathy and eventual death.

133. (E) Transduction is a technique whereby DNA is packaged into

lysogenic phages for transfer to other susceptible cells. It exists in two
forms: transfer of specific sequences, known as specialized transduction,
and transfer of random sequences, known as generalized transduction.

134. (B) Halogens are known for their affinity to attract electrons from
other atoms. When halogens target atoms contained within organic
materials, the loss of electrons can cause significant changes in the
materials’ tertiary structure. This causes denaturation of proteins, loss of
protein function, and eventual death of the dysfunctional cell.

135. (A) An infectious agent that presents with a complex protein is either a
virus or a prion. The question provides a classic description of a complex
bacteriophage such as T4.

136. (A) Horizontal transfer of DNA refers to the movement of genes from
cell to unrelated cell, perhaps even to a different species. The horizontal
transfer of resistance plasmids, with the coding for multiple drug resistance,
is identified in answer A.

Chapter 5: The Eukaryotic Cell

137. (D) All cell membranes contains proteins, phospholipids, and
glycoproteins that are specific for a species, so there are some minor
variations within the exact component structure. Only answer D is the most
complete and the correct choice.

138. (D) People often associate an increasing number of chromosomes with

the resulting complexity of the organism. However, a mosquito has 6
chromosomes; a locust, 10; a pea, 14; a toad, 20; a lungfish, 38; a human,
46; a rabbit, 66; a pigeon, 80; a willow tree, 152; and a king crab, 208.

139. (A) Small uncharged molecules such as O2, CO2, and water pass
through a membrane impeded by simple diffusion and always in the
direction of the gradient from higher to lower concentrations.

140. (B) The protein in the question is one with multiple hydrophobic
regions. These regions fold back and forth through both leaflets of a cell
membrane, producing a large, pore-shaped structure shaped like a barrel
and functioning as a transmembrane protein.

141. (C) A cytoskeleton is composed of an array of protein microfilaments.

The diameter of these microfilaments places them well below the level of
resolution for a light microscope. X-ray crystallography may perhaps be
used to determine the structure of the microfilament molecules but not the
cytoskeleton itself.

142. (E) Mitosis is the portion of the cell cycle in which the cell actually
undergoes cellular division by cytokinesis. Answer E shows mitosis proper,
when the tetraploid genome separates into two identical diploid daughter
nuclei.

143. (C) Vesicles associated with cellular manufacturing are formed at

regions of the ER furthest from the nucleus, where they bud off and move
to the nearby Golgi apparatus. Here, their contents are further modified and
structurally completed for their cellular function.

144. (E) Small charged ions such as Ca2+, Na+, and Cl− cannot pass through
the hydrophobic and uncharged regions in the interior of a cell membrane
unless a protein with a secondary structure forms a transmembrane α-helix
through which specific ions can flow.

145. (E) A cytoskeleton, composed of protein microfilaments, is

responsible for maintaining cell structure and providing a framework for
intracellular transport. Cytoskeletons are universally found within all
eukaryotic cells and have also recently been discovered in some bacteria as
well.

146. (A) The fluidity of a membrane is a measure of its rigidity; the more
fluid the membrane, the less rigid it is. Irregularity increases fluidity.
Unsaturated fatty acids are kinked and inhibit close packing. Decreasing the
lengths of these fatty acids would decrease density and increase fluidity.

147. (B) An aneuploidy cell, even while in G0, will have DNA content
other than diploid, indicating chromosomal aberrations. Translocation can
produce aneuploidy by an improper distribution of chromosome parts;
nondisjunction produces aneuploidy by an improper assortment of whole
chromosomes; and trisomy represents a cell with at least one extra set of
chromosomes.

148. (E) Motions commonly observed and measured include lateral

movement; rotation around the longitudinal axis at up to 30,000 rpm;
bending of the fatty acid tail; and the much more infrequent flip-flop from
one leaflet to the other. What does not occur, however, is a reversal of the
hydrophilic phospholipid head from the outside of the membrane to the
strongly hydrophobic middle interface between the two leaflets.

149. (A) The only gated transport of substances into the cell is through ion
channels much too small for proteins. Substances, including ribosomal
proteins and enzymes synthesized in the cytosol, are escorted into the
nucleus via gated nuclear transport.

150. (D) A cytoskeleton is composed of three primary protein components:

the small microfilaments (MF) with diameters of about 7 nm, the larger
intermediate filaments (IF) that are 6 to 12 nm in diameter, and the even
larger microtubules (MT) with a diameter of 15 nm on the inside and 25 nm
on the outside.
151. (D) A glucose molecule is too large to pass through a membrane
without significant protein assistance. Although coupled transport can be
used to transport glucose, it is effective only when transport is with the
gradient. The loading of glucose from the intestinal lumen, where the
glucose level is low, into an epithelial cell, where the level is higher,
requires carrier-mediated active transport.

152. (B) A peculiarity of fatty acid synthesis is that the molecules always
contain an even number of carbon atoms. The membrane diglyceride tails
are 18 to 20 carbon atoms in length. If they were longer, the membrane
would become too inflexible and of insufficient fluidity to allow most vital
nutrients to pass through.

153. (A) A special signal sequence of amino acids directs a protein being
synthesized in the cytosol attachment to receptor proteins unique to the
chloroplast. Once attached, the ribosome-protein-receptor assembly moves
laterally along the surface of the chloroplast until it encounters a transport
protein. The signal sequence and the remainder of the newly synthesized
protein then pass through the opening to the interior of the chloroplast,
where the protein begins to refold into its functioning tertiary configuration.
Once complete and released from the ribosome, the signal sequence is
removed.

154. (C) Translation always takes place in the cytosol. The resulting
ribosomal proteins are then escorted back into the nucleus. Ribosomal RNA
is then transcribed, and it congregates with the imported ribosomal proteins
to form the ribosomal subunits.

155. (D) The sudden influx of calcium ions from the sarcolemma of muscle
cells into the cytosol—which changes the actin-myosin interaction and
produces the classic muscle contraction—is enabled by the much higher
concentration of these ions outside the cell than inside it. To precipitate
sufficient ion shift, the differential has to be on the order of 10,000:1.

156. (B) As part of cytokinesis, centrioles are manufactured during G2

phase of interphase, just prior to mitosis. These act as microtubule
organizing centers (MTOCs) for the production of the mitotic apparatus.
The structures associated with the retraction of chromatids from the cellular
equatorial plane toward the centrioles are microtubules.

157. (E) The cell cycle is divided into interphase and mitosis, with most of
the time spent in interphase. Once the cell reaches a critical mass, a signal
initiates the process that leads to cellular division. As the cell leaves G0
phase, it begins to synthesize the enzymes and proteins needed for DNA
replication during G1. After G1, replication takes place during S phase.

158. (C) Glycosylation is a process that is a part of normal cellular function

and is observable in proteins that are synthesized throughout G0 phase. The
degree of glycosylation has no effect on membrane permeability, as these
structures are always located on the exterior leaflet. These membrane
proteins are no more or less likely to be cross-linked than any other protein.

159. (B) Often, when synthesized into the lumen of the endoplasmic
reticulum, the activity of the new protein is dependent on folding differently
from its lowest energy requiring form. To overcome this issue with the
second law of thermodynamics, special chaperone proteins assist the
folding.

160. (E) Microfilaments, the thinnest of the cytoskeletal framework

proteins, are responsible for a number of cellular functions. These include
movement within the interior of the cell, contraction of the cleavage furrow
prior to the completion of cytokinesis and cellular division, shaping the cell,
and participation in muscle cell contraction.

161. (E) The endosymbiotic theory hypothesizes that the two metabolic
organelles of eukaryotic cells, the chloroplast and the mitochondrion, are
descendants of bacteria that began a symbiotic relationship with a primitive
nucleated cell in antiquity. Lines of support—as in answers A, B, C, and D
—increase the acceptability of this theory.

162. (A) Chromatin condenses and the sister chromatids join at the
centromeres during prophase. The nuclear membrane dissolves and the
mitotic spindles form during prometaphase. The chromosome pairs align on
the equatorial plane during metaphase. During anaphase, the sister
chromatids are separated by microtubules. Lastly, during telophase, the
chromosomes relax back into their chromatin form and the nuclear
envelope reforms.

163. (B) Apoptosis is a regimented and controlled mechanism triggered by

attachment of a signal protein. The cell first prepares its nuclear contents for
neat destruction followed by the processing of its cytosol. When completed,
the neatly packaged and degraded materials are easily cleaned up and
disposed of by macrophages with no adjacent tissue damage.

164. (C) Because the nucleus initiates the process that ends with protein
synthesis, it stays in close proximity to the endoplasmic reticulum. The
DNA is anchored to the inner nuclear lamina. The passage of materials into
or out of the nucleus is tightly controlled with nuclear pores that are not
simple barrel proteins but rather large complexes of more than 100
components.

165. (D) The level of glucose within the intestinal epithelial cell is greater
than that in both the intestinal lumen and the tissues inside the body
opposite the lumen. Because the sodium levels are much higher in the
lumen than in the cell, the strong flow of Na+ into the cell is harnessed to
bring in glucose as well by symport, not in the reverse direction.

166. (A) Glycolysis, the breakdown of glucose into two molecules of

pyruvate, takes place within the cytosol. The high-energy electrons
harvested during this process and the TCA cycle are used to reduce NAD to
NADH, which then carries these electrons to the mitochondria where they
produce 36 ATP per glucose molecule.

167. (A) Centrioles are on both extremes, eliminating answers C, D, and E.

A centrosome is the structure that contains the centromeres. During
prometaphase, special protein structures called kinetochores are assembled
on the sides of the chromosomal centromeres, whereas answer B incorrectly
identifies them as centrosomes.

168. (D) Cancers are precipitated by some form of mutagenesis, followed

by increased sensitivity to and production of growth factors and a loss of
sensitivity to downward growth signals. The fail-safe, activation of
apoptosis, is lost as well. One factor that greatly enhances tumor growth is
angiogenesis, but this does not occur in all cancers.

169. (D) The number of specific organelles within a cell depends on the
peculiar functions required by that cell. Cells requiring high energy
production and high oxygen availability, such as neurons, may well contain
thousands of mitochondria so as to be sufficiently powered.

170. (B) The ER is one vast, highly convoluted structure that is continuous
from the nuclear envelope to the regions adjacent to the Golgi apparatus.
The RER is found closer to the nucleus and is the region where ribosomes
congregate to synthesize proteins into the ER. The SER is free of simple
ribosomes and is the region where protein modifications take place.

171. (B) The nucleolus, which occupies about 25 percent of the nuclear
volume, is the site of transcription of rRNA and the area of the assembly of
ribosomal subunits.

172. (E) The lysosome contains more than 40 inert enzymes and
compounds that become active when it fuses with a phagosome containing
larger cell-sized materials and becomes a cellular version of a stomach.

173. (E) Apoptosis is programmed cell death. It can be triggered from the
outside by the attachment of a signal molecule such as Fas or TNF-a to
what is morbidly known as a death receptor. Alternately, the release of
cytochrome c from a damaged mitochondrion, which binds to cytosolic
proteins to produce an activating apoptosome, can also initiate the process.
Either activation sequence then generates a series of caspases that complete
the process.

174. (A) The nucleus serves as the repository of genetic information.

Signals from outside the cell generate messengers that pass into the nucleus
and serve to decide what “pages” of code will be transcribed from the form
of DNA into the form of RNA. These transcripts are then transferred
outside the nucleus, where they are translated into the language of proteins
for form and function. The concept of storing information best describes a
library.
175. (C) Cells communicate with each other by ligand-receptor interactions.
The binding of a ligand to a membrane protein triggers conformational
changes in the receptor on the cytosolic side of the membrane, which in
turn produces second messengers that then serve to produce changes in
gene expression. Antibodies can block this ligand-receptor interaction.

176. (C) Small, uncharged, hydrophobic molecules can pass through a cell
membrane unimpeded. Slightly larger, uncharged, polar molecules can pass
through a membrane and require regulation. Large, uncharged molecules
require carrier assistance to pass through the membrane. The membrane is
impervious to the passage of ions that require gated proteins to permit their
passage.

177. (B) Proteins may be embedded in the membrane or simply attached to

it in order to perform their function. Embedded proteins serve as carriers,
anchors for the cytoskeleton, and receptors for cell communication
molecules. The only thing membrane-bound proteins are not associated
with is storing substances, which would best be accomplished by vesicles.

178. (D) Water is a small, uncharged, polar molecule that always passes
through a membrane in the direction of a gradient freely and thus requires
regulation but cannot be moved by active transport.

179. (D) One of the most common secondary protein structures assumed
during synthesis is the a-helix, which is observed as a tight coil.
Hydrophobic amino acids are usually coiled as an a-helix into the
hydrophobic interior of the membrane. These structures can pack closely,
because their hydrophobic side chains are distributed to the membrane
associated outside of the protein.

180. (D) The cell’s cytoskeleton is best associated with structure and
movement. The import of LDL is by membrane fusion and has no
cytoskeletal involvement.

181. (A) For a multicellular organism to maintain homeostasis, it must be

able to form a barrier between itself and the hostile outside world. The cells
of this barrier must be able to remain tightly bound to each other (as in
answers B and D). Answers C and E represent the adhesive structures that
also serve as conduits for the movement of molecules from cell to cell.

Chapter 6: Specialized Cells and Tissues

182. (A) Theodor Schwann’s studies in the mid-nineteenth century
identified cells that surround neurons in certain nervous tissues. These cells
were later identified as being important in the production of the myelin
sheath that improves nerve action potential transmission. These cells are
now called Schwann cells.

183. (D) Muscles are responsible for motion. When observed under a
microscope, actin and myosin protein filaments slide past each other,
shortening the muscle cell and producing muscle contraction by a
mechanism called the sliding filament model.

184. (C) In muscle cells, the regular array of thick myosin filaments
comprise the bulk of the dark A band. The overlapping proteins of thin
actin connect together in the Z disk, which is observed as the lighter I band.
Sarcomere is a term used to define the muscle contractile unit between Z
lines (or Z disks). When calcium ions flood the muscle cells, they interact
with troponin and permit the actin to interact with myosin to precipitate
muscle contraction.

185. (D) Neurotransmitters are chemicals that brain cells and other nervous
tissues use to communicate with each other. A neurotransmitter has no
effect on a cell unless the receiving cell has a receptor specific for that
neurotransmitter. Acetylcholine is the neurotransmitter most commonly
used to signal a muscle to contract.

186. (B) Ion channels at the location of a neuron stimulus open, allowing a
flood of sodium ions into the cell. This flood changes the resting potential
charge polarity on the membrane, reversing it from −70 mV to +30 mV. As
the depolarization spreads out from the original source, the initial gates
close and sodium-potassium pumps rapidly restore the sodium imbalance of
the action potential back to −70 mV.
187. (C) A typical neuron consists of the cell body, numerous projections
from the cell body called dendrites, and a single long axon. The nucleus
resides in the major portion of the cell—the cell body.

188. (E) Mitochondria are the powerhouses of the cell. The more energetic
the cell, the greater the number of mitochondria required to supply that
energy in the form of ATP. The cells requiring the greatest level of ATP use
are neurons and muscle cells.

189. (B) The basic cell of the nervous system is the neuron. This eliminates
answer A. The axons of nerve cells, not entire cells, are covered in myelin,
which eliminates answer E as well. A nerve is a cluster of long axons,
eliminating answers C and D and making answer B the best description.

190. (B) Striations refer to the striped appearance of the two striated muscle
tissues: skeletal and cardiac. An individual muscle cell, also known as a
myofibril or a muscle fiber, is filled with cytosol called the sarcoplasm.
Surrounding the cell and containing its nucleus is the sarcolemma, or cell
membrane.

191. (A) A bone consists of a calcium and phosphate matrix. Within this
matrix reside osteoblasts that are responsible for depositing the mineral
content of the matrix. When these cells are surrounded, they remain in the
lacunae and are identified as osteocytes. If some damage happens to the
bony structure and fragmentation occurs, osteoclasts start roving through
the debris, dissolving the matrix.

192. (E) Sodium ions leak into a cell, so it must expend about 30 percent of
its ATP pumping them back out. However, to maintain the proper charge
within the cell, potassium must be imported at the same time the sodium
leaves by antiport at a ratio of three sodium ions out for every two
potassium ions in. This can only occur because the potassium levels inside
the cell are much higher than those outside in the tissues.

193. (C) In muscle cells, the cytosol is referred to as the sarcoplasm. Within
the sarcoplasm is a convoluted network of membranes known as the
sarcoplasmic reticulum. Mitochondria and endosomes (answers D and B)
can be eliminated from consideration because they do not form networks.
While the remaining answers are associated with a network structure, the
sarcoplasmic reticulum is not near ribosomes (answer E) and does not form
vesicles (answer A).

194. (D) An axon is the lengthy extension of a neuron and serves as a

conduit for signal propagation. The threshold for generating an action
potential is established within either dendritic connections to other nerve
cells or by other cell dendritic connections to the cell body.

195. (E) Epithelium is a tissue that serves primarily as a lining or separation

barrier. Squamous cells are flat and thin, much like a shape of a shield.
Keratin is a protein designed to provide an impenetrable barrier. Epithelial
tissues composed of overlapping, shieldlike, squamous cells that contain
keratin function best as a barrier that allows nothing in or out, as with the
skin.

196. (A) Nerve impulses are sent down the axon in the form of an action
potential. However, if the surface is covered with insulating myelin, then
the action potential leaps from node to node in a much more rapid and
energy-efficient manner, because only the gaps in insulation at the nodes are
subject to the polarization-depolarization cycle.

197. (A) There are three forms of muscle cells. Smooth muscle cells are
spindle shaped, lack striations, and provide slow and continuous
contractions. Skeletal muscle cells are arranged in bundles, are striated, and
provide for rapid but short-lived contractions. Cardiac muscle cells are
branched, are striated, and serve to provide short and rapid contractions
over an extended period of time, and their nuclei are located similarly to
those in skeletal muscle.

198. (B) Transcription is the process of producing an mRNA transcript of a

DNA-based gene code and takes place only in the nucleus. The only cell
that would be incapable of transcription would be one that lacks a nucleus,
such as a red blood cell.

199. (D) An inactive neuron has a resting potential of −70 mV. When the
cell receives a signal, the ligand attaches at a receptor, which then opens a
ligand-gated channel. The influx of ions—in this case, sodium—then causes
adjacent voltage-gated channel proteins to open, increasing the sodium
influx. This influx changes the local charge differential from −70 mV to
+30 mV and is known as the depolarization phase.

200. (A) The cell cycle consists of interphase, which occupies about 90
percent of the life cycle (when most metabolism, cell growth, and
maintenance occur) and M phase just prior to cell division. Cells that do not
need to divide include neurons and unreactivated lymphoid memory cells.

201. (C) Neurotransmitters are chemicals that will activate ligand-gated

channels in cells on the postsynaptic side of a synapse. Acetylcholine
predominates in the neuromuscular junction. Norepinephrine is found in
both the central and peripheral nervous systems. Serotonin and amino acids,
which include GABA, are found only in the brain.

202. (E) Calcium interacts with troponin, which then uncovers myosin
binding sites on the tropomyosin strands that are interwoven along a
backbone of actin on the thin filament. This then permits the myosin, which
makes up the bulk of the thick filament, to repetitively bind and detach
from the binding sites, producing a walking effect that contracts the
sarcomere. Thus, all of these components except myosin are on the thin
filament.

203. (C) Ion channels are proteins that permit the passage of specific ions
through a membrane, always in the direction of a gradient. These channels
are gated, meaning they can be either open or closed. In neurons, the action
potential is propagated down the neuron by the actions of voltage-gated
channel proteins.

204. (D) For the muscle to relax following contraction, the bound
neurotransmitter acetylcholine is broken down by acetylcholinesterase and
recycled back to the neuron. Nerve agents are cholinesterase inhibitors that
prevent the enzyme from breaking down the bound neurotransmitter.

205. (B) Both Schwann cells and oligodendrocytes are associated with the
production of the myelin sheath surrounding neuron axons, but the former
are only found in the peripheral nervous system. The presence of
oligodendrocytes results in white matter.
206. (A) An inhibitory neuron produces a dampening effect to prevent the
formation of an action potential in an adjacent neuron. One of the best ways
to counteract a buildup of positive charges in a cell as the result of a signal
from a stimulatory neuron is to produce a concomitant influx of negative
charges, such as Cl− ions. Thus, when a cell receives balanced stimulatory
and inhibitory signals, the net result is no action within the receiving cell.

207. (B) Steroid hormones enter all cells directly through the membrane
and act as DNA binding proteins after binding to a cytosolic receptor.
Protein hormones, however, only affect cells that express the receptor
protein specific for that hormone. In this case, changing the hormone might
produce the desired response.

208. (E) Cells that require high levels of energy use have higher numbers of
mitochondria in the cytosol to produce that energy. Muscle cells, which are
responsible for contraction, have a much higher level of actin and myosin
than other cells. So it is not surprising that the cells of the organ responsible
for blood detoxification, the liver, has much higher levels of the cellular
organelles associated with breaking down toxic materials.

209. (C) Generally, chemotherapeutic drugs interfere with the rapid,

uncontrolled cell division of cancer cells by interfering with DNA
replication. Unfortunately, humans have cells that divide frequently because
they continually need to replace other cells. One of the pronounced side
effects of chemotherapy is hair loss caused by damage to skin cells.

210. (A) Moderate fever in response to a bacterial infection is a good thing.

The elevated body temperature inhibits bacterial replication and increases
the binding of iron by serum proteins. Bacteria frequently enter the body
through wounds, so the increased growth rate of fibroblasts—and thus, their
more effective role in healing—is also accelerated by fever.

211. (D) If there is a shortfall of calcium release, such as might occur if

there is leakage out of the cell, there can be an insufficient interaction with
troponin, resulting in the uncovering of fewer myosin binding sites and
reduced muscle contraction force. This calcium leakage is known to occur
in the elderly, who lose muscle strength even when doing weight training.
212. (E) Of the tissues identified, cartilage is the slowest healing because
the chondrocytes are bound in a tight matrix with few nutritional resources.

213. (E) Connective tissue is one of the four major tissue classifications
within the body and comprises about 25 percent of body mass. It includes
cartilage, bone, adipose tissue, lymphatic and blood components, and
collagen. The other three major types of tissue are epithelial, nervous, and
muscle.

214. (C) The fetal gastrula differentiates into the ectoderm, endoderm, and
mesoderm. The ectoderm gives rise to the epidermis and nervous system.
The endoderm gives rise to glands and the lining of the lungs and
gastrointestinal system. The mesoderm gives rise to the dermis, circulatory
system, skeletal system, muscle, gonads, and excretory system.

215. (D) Epithelial tissue lines organs and tissues. This includes the skin as
well as organ coverings. Because they are associated with protection, the
cells comprising these tissues are organized and layered. Although answer
E might seem out of place, exocrine glands are derived from epithelial
tissues. Complex columnar epithelium does not exist.

216. (B) A structure described as reticular (or network) would represent a

loose organization, not condensed as in answers C and D. The matrix
supporting adipose tissue is well defined and not diffuse (answer E). While
blood vessels might present on the surface as spider veins, the interior
lining is actually quite enclosed, otherwise the blood would leak out of the
capillaries and other blood vessels, making answer A a poor choice.

217. (B) Connective tissue is composed of many fibrous proteins, cells, and
substances—including water—associated with filling spaces. Common
materials included in connective tissue include those identified in answers
A, C, D, and E. While a tendon is considered a connective tissue, it is not a
material that makes up connective tissue.

218. (C) Goblet cells are found in the epithelial lining of organs. These cells
secrete mucin. Mucus (hydrated mucin) functions as a lubricant and a
component associated with protecting surfaces from microbial invasion by
trapping microorganisms and dust. Goblet cells are thus found in the trachea
and bronchioles of the lungs, in the luminal lining of the small and large
intestines, and in the conjunctiva of the eyes—but not in the kidneys.

219. (A) M cells are macrophage-derived cells. What glial cells are to
nervous tissue and what macrophages are to bone, cartilage, and muscle, M
cells are to the small intestine.

220. (D) Glial cells, found in the brain, are responsible for nutritional and
structural support and the protection of neurons in the white matter.

221. (E) The body uses adipose tissue for protection and as an energy
resource. This tissue is composed of adipocytes, which are storehouses of
high energy–containing lipids.

222. (A) The bones are the primary storage material for both phosphate and
calcium.

223. (D) The hypothalamus passes neural signals to the pituitary gland,
which in turn secretes hormones that affect the body as a whole, including
the hypothalamus.

224. (A) The structures listed in this question are cell-to-cell joining
structures. They are best associated with very tight adhesions usually
present to prevent cell separation caused by high-abrasion conditions. Skin
is subject to all sorts of abuse and abrasion that would shred the tissues if its
cells were loosely connected.

Chapter 7: The Nervous and Endocrine Systems

225. (B) The nervous system is divided up into two broad sections: the
central nervous system (CNS) and the peripheral nervous system (PNS).
The nerves within the vertebrae, known as the spinal cord, are part of the
CNS, which also includes the brain and brain stem.

226. (C) The myelin sheath provides insulation and increases the speed of
the action potential down an axon. Additionally, when damage occurs, the
sheath assists in neuron repair.
227. (A) The action potential travels down a noninsulated axon as charge-
gated ion channels open and close rapidly in response to the flood of ions
along its length. Since ion flow across the axon membrane is impeded by
the myelin sheath, there is no need to have ion channels anywhere other
than at the nodes.

228. (C) When blood calcium levels drop, the parathyroid glands release
parathyroid hormone (PTH) that stimulates osteoclasts in the bone to
release calcium, cause the kidneys to reabsorb more calcium, and increase
calcium absorption in the intestinal tract.

229. (E) Type 2, or adult-onset, diabetes is frequently attributed to a loss of

insulin sensitivity or excessive absorption by adipose tissue in obese
individuals. In type 1, or juvenile-onset, diabetes, the β cells of the pancreas
are incapable of secreting insulin.

230. (E) When the body is under stress, the hypothalamus secretes
corticotropin-releasing hormone (CRH) that stimulates the anterior pituitary
to release adrenocorticotropic hormone (ACTH). This, in turn, signals the
adrenals to produce corticosteroids such as cortisol (or hydrocortisone),
synthesized from cholesterol, that increase blood sugar levels and energy-
releasing metabolism.

231. (D) When a neuron receives an appropriate stimulus in the form of a

neurotransmitter or mechanically gated signal, there is a sudden influx of
sodium ions (Na+). This eliminates answers A, C, and E. Sodium-potassium
pumps restore the original resting potential by bringing the leaked sodium
back out and the escaped potassium back in, contrary to answer B.

232. (C) Every time a neuron conducts an action potential along its axon,
the sodium and potassium balance of the resting potential must be restored
in order for the cell to be able to send another signal, which requires huge
quantities of ATP to power the sodium-potassium pumps. For this reason,
neurons contain thousands of energy-generating mitochondria, which in
turn require huge quantities of oxygen and glucose.

233. (A) The anterior pituitary releases thyroid-stimulating hormone (TSH),

which stimulates the thyroid to release triiodothyronine and thyroxine (or
T3 and T4, respectively). This, in turn, increases metabolic output and
protein synthesis.

234. (D) The fight-or-flight response prepares the body for immediate
action by constricting blood vessels and increasing heart rate, thus raising
blood pressure and blood output. Epinephrine and norepinephrine, released
by the adrenal glands, produce the effects that can help the body survive
crisis conditions.

235. (B) Nonsteroidal, or peptide, hormones bind to receptors on the cell

surface if they are present. This ligand-receptor interaction induces a
conformational change in the receptor, which modifies the cytosolic
structure. This change produces a second messenger such as cyclic AMP
(cAMP) that then causes the production of a DNA binding protein that
changes genetic expression.

236. (A) In reference to the brain, a ventricle is a space that contains

cerebrospinal fluid, which is essential for cushioning the brain from trauma
but is not associated with the meninges aside from their protective function.
The arachnoid and dura mater are layers of the meninges, but sulcus refers
to a depression or fissure of the brain surface.

237. (D) The spinal cord is divided into five regions, all of which are
associated with the control of everything below the head, and the nerves
generally descend downward from the spine. The vagus nerve, which
stimulates the viscera, is included as one of the cranial nerves originating
from the brain stem.

238. (E) Oxytocin—responsible for cervical dilation and uterine

contractions during childbirth and for feelings of contentment and
fulfillment leading to bonding afterward—and antidiuretic hormone (ADH,
also known as vasopressin), which regulates fluid balance throughout the
body, are both synthesized within the hypothalamus but are stored and
released by the posterior pituitary as necessary.

239. (B) Aldosterone, after production in the adrenal cortex, increases

sodium reabsorption in the kidneys while simultaneously decreasing
reabsorption of potassium. This rise in sodium ion concentration increases
water retention and blood volume, which also increases blood pressure.

240. (A) Iodine is an essential element that is normally acquired from

seafood or iodized salt. When ingested, it is transferred to the thyroid,
where it is incorporated into both T3 and T4. These hormones increase
growth, development, and metabolism. When iodine uptake is insufficient,
the thyroid attempts to compensate by enlarging in size, which produces a
goiter.

241. (B) Glial cells provide both immune surveillance and production of the
myelin sheath. The subarachnoid space is filled with cerebrospinal fluid.
The two hemispheres of the brain are connected by the corpus callosum,
which is a fluid-filled ventricle in the central portion of the brain. This
plexus is responsible for production of the cushioning CSF, which fills the
ventricles and space surrounding the brain.

242. (C) Gamma-aminobutyric acid (GABA, or γ-aminobutyric acid) is a

neurotransmitter that opens chlorine ion channels, producing a flood of
negative charges into the cell, which negates the signal threshold produced
by a stimulatory influx of sodium ions. As such, it serves to inhibit signal
transduction and has a role in reducing the perception of pain.

243. (D) Both the thyroid and adrenals are controlled by the anterior
pituitary, but ADH and oxytocin are produced by the posterior pituitary.
These glands are all controlled by the hypothalamus.

244. (A) The autonomic nervous system (ANS) is composed of two

branches: the sympathetic nervous system and the counterbalancing
parasympathetic system. Although the two work together to provide
consistent functioning of the body as a whole, they are not anatomical
mirror images of each other. So even though the cranial nerves stimulate the
digestive processes of the viscera, their counterparts in function are the
thoracic nerves, which inhibit digestion.

245. (C) There are two basic types of hormones: steroid and protein. While
a steroidal hormone passes through a cell membrane, its effect on the cell is
at the nuclear transcription level after it has bound to an appropriate
receptor.

246. (B) During fetal neurological development, the brain initially forms
three parts: roughly the fore-, mid-, and hindbrain. Later differentiation of
the forebrain produces the recognizable structures of the thalamus,
hypothalamus, and cerebrum as well as others. The cerebrum encloses the
interior lining structure of the limbic system.

247. (E) The period of rapid eye movement (REM) is controlled directly by
brain function. REM is a stage of sleep that comprises about 25 percent of
human sleeping time.

248. (E) Long-term stress keeps the body in a state of perpetual charge that
produces damage if unrelieved. This includes damage to organs due to
elevated blood pressure, ion imbalance, and adrenal exhaustion due to the
overactivity of the hormone-producing cells of the cortex and medulla.
There is also a depletion of energy reserves due to excessive metabolic
output.

249. (E) Alcohol may give the appearance of a CNS stimulant because of
the commonly observed increase in erratic behavior, but its effect is actually
as a depressant of behavioral inhibitions. When consumed in excessive
quantities, it suppresses brain and other function to the point of inducing
coma and death.

250. (D) Suckling produces a comforting feeling in the mother and thus is
not associated with stress or related signals that produce ACTH or human
growth hormone (HGH). Oxytocin produces a tremendous sense of well-
being and contentment that increases the bonding experience.

251. (D) Olfactory nerves relay signals from the nose to the olfactory bulb
of the limbic system and provide for the sense of smell.

252. (A) Amyloid plaques are associated with Alzheimer’s disease, not
senile dementia, so answer B can be ignored. Loss of speech is best
associated with semantic dementia, so answer C is incorrect. Senile
dementia is best described in answer A and is different from the normal
effects of aging seen in answers D and E.
253. (D) The cholesterol molecule serves as a core molecule for the
synthesis of many important substances, including vitamin D, aldosterone,
testosterone, estrogen, progesterone, and cortisol. Only ACTH is different,
as it is synthesized from pre-proopiomelanocortin (pre-POMC).

254. (E) Excessive insulin drops the blood glucose levels to dangerous lows
and causes what is known as insulin shock, resulting in dizziness,
trembling, fainting, and possible seizures. The most rapid treatment to
counter the depressed glucose levels is to increase sugar levels, commonly
by simply eating a candy bar.

255. (C) When blood glucose levels are low, glucagon is secreted by the a
cells, which stimulates the liver to break down glycogen stores and release
glucose. When blood glucose levels are high, insulin is secreted by the β
cells, which comprise about 75 percent of the islet cells. This makes answer
C the correct choice.

256. (C) The only real difference, other than their mechanism of synthesis,
is their size. The two forms of enkephalins are both pentapeptides, while the
four types of endorphins range in size from 16 to 21 amino acids in length.

257. (B) About 5,000 taste buds line the lingual epithelium of the tongue.
The taste receptor cells within these organs bind specific molecular
components of foods. When triggered, the afferent nerves signal the brain
through the seventh and ninth cranial nerves. There are currently five
recognized flavor sensations: sweet, bitter, savory (or umami), salty, and
sour.

258. (A) ADH is an abbreviation for antidiuretic hormone, also known as

arginine vasopressin (AVP) or simply vasopressin. This peptide hormone is
a regulator of blood salts that affect fluid balance and blood pressure.
Although it is released from storage in the posterior pituitary, it is actually
produced within the hypothalamus.

259. (D) A stroke may be caused by a blood clot that blocks the flow of
blood and oxygen to portions of the brain or by the rupture of a blood vessel
that produces a hemorrhage, which also prevents oxygen from reaching
portions of the brain. This type of brain injury is also known as a
cerebrovascular accident (CVA).

260. (B) Stress stimulates the release of adrenal hormones. While the
pancreas is in charge of short-term glucose control, the adrenals also
produce glucocorticoids and adrenaline, which can affect both blood
pressure and blood sugar levels. While the adrenals can affect the rate of
protein catabolism with some energy release, they do not upregulate
metabolism like thyroid hormones do.

261. (C) The pons is inferior to the midbrain and controls mainly sleep,
equilibrium, eye movement, taste, and swallowing. Answers A, B and E are
best associated with higher brain functions. The bottom half of the brain
stem is the medulla oblongata and is responsible for breathing, heart rate,
and blood pressure.

262. (A) The parasympathetic system is the counterbalance to the

sympathetic system and is controlled primarily within the brain stem. It
triggers increased digestion (more saliva, peristalsis, gastric secretion,
defecation, and bile production); pupil constriction; reduced heart effort and
blood pressure; urination; and bronchoconstriction.

263. (B) The word otolith is used to describe the very small clusters of
calcium carbonate within a gel-like matrix in the inner ear. When the head
is subject to motion, the matrix shifts on hair-cell projections due to
momentum, providing the brain with a sense of motion. Based on these
signals, portions of the brain stem make adjustments in posture and body
position to maintain balance.

264. (E) Nearsightedness (also known as myopia or shortsightedness) is a

condition in which the eyeball is more elongated and the optical length is
shorter. Images focus in front of the retina. People with this condition can
see near objects more clearly than those that are distant.

265. (E) Many animals use regurgitation as a voluntary process for feeding
their young. Micturition, or urination, is under voluntary control. The fight-
or-flight response is really the culmination of a series of physiological
responses under involuntary control but is not as rapid as required by the
question. Peristalsis is under autonomic control. The question best describes
what is known as a reflex.

Chapter 8: The Circulatory, Lymphatic, and Immune Systems

266. (C) The immune system is composed of primary and secondary
lymphoid organs. Both the thymus (a primary organ) and the spleen (a
secondary organ) are the largest of the group. Lymph nodes are the next
smallest in size and are more complex and organized than the remaining
two. Of the remaining answers, lymph nodules are collections of lymph
follicles.

267. (D) As arterial vessels get farther from the heart, they get smaller,
becoming arterioles and then tissue capillaries. As the blood returns to the
heart, it flows first through venules and then through veins before passing
through the vena cava back into the heart.

268. (B) Neither erythrocytes nor lymphocytes are phagocytic. The three
remaining choices are, but eosinophils are only slightly so and are few in
number. Macrophages are larger than neutrophils, and each are capable of
phagocytosing more per cell than eosinophils; however, neutrophils
outnumber macrophages by more than 3:1.

269. (E) If blood is withdrawn from the body, it immediately begins to clot.
The straw-colored liquid that remains is called serum. However, if blood is
drawn into a tube containing an anticoagulant, the clotting proteins remain
in the fluid phase. After the cells settle, the straw-colored liquid that
remains is called plasma. Serum is plasma with the clotting proteins
removed.

270. (A) Immunoglobulin is another name for an antibody. Once these

glycoproteins are synthesized in lymph tissues, they circulate first through
the lymph and then through the blood. They are composed of four protein
chains, which are identified as two light chains and two heavy chains bound
together by disulfide bridges.

271. (A) The immune system is divided into primary and secondary
lymphoid organs or tissues. The primary organs are responsible for
generating and screening the cells of the immune system. The organs
responsible for initially manufacturing these cells are the thymus and bone
marrow.

272. (D) Blood enters the right side of the heart at the upper chamber, the
right atrium. It then passes into the lower chamber, the right ventricle. From
the right ventricle, it flows through the lungs and becomes oxygenated,
returning into the left atrium. It passes from there to the left ventricle, where
it is then pumped out to the body.

273. (D) Complement is a complex of normally inactive proteins circulating

in the blood. When activated, a complex known as C1 begins a cascading
series of reactions that cleave the inactive forms of these proteins to active
forms, one after another, ultimately producing an attack complex that drills
holes through the cell membrane and causes lysis.

274. (C) Vessels that lead blood away from the heart are arteries; vessels
that return blood to the heart are veins. The blood that leaves the right
ventricle goes to the lungs through the pulmonary arteries with very little
oxygen remaining. After the blood becomes as oxygenated as possible, it
leaves the lungs to return to the heart through the pulmonary veins.

275. (C) When a cell becomes cancerous, it usually starts to express

proteins that are normally not expressed by normal cells, and these can
stimulate a specific immune response. The effector cells that attack cancer
cells by inducing apoptosis are known as cytotoxic T lymphocytes, or killer
T cells.

276. (B) The only thing listed that the lymph does not do is produce
antibodies; that is done by B cells and plasma cells congregated in the
lymphoid tissues they pass through.

277. (B) A sphygmomanometer is a device that uses a pressure cuff to

measure systolic and diastolic blood pressure in millimeters of mercury.

278. (E) Macrophages flowing through the blood bounce into ligands and
begin to marginate—first slowly, as a rolling adhesion, then the cells
become more firmly attached by tighter binding with additional molecules.
Once this stops, the cells enter the tissues by going between adjacent
endothelial cells (diapedesis). Once there, they migrate through the tissues
toward the infected area following a signal gradient.

279. (E) Bone marrow stem cells initially differentiate into myeloid and
lymphoid progenitor cells. Erythroid progenitor cells then degenerate into
erythrocytes (or red blood cells).

280. (A) When a foreign antigen binds to the surface-bound antibody, it

activates the B-cell response. First, the cell undergoes lymphoproliferation,
producing a clone of cells that all produce the same antibody. Second, these
cells all shift to manufacturing secreted antibodies. Some of them become
memory cells and the remainder differentiate into antibody factories known
as plasma cells.

281. (C) Since all areas of the body are susceptible to attack from microbial
invaders, the immune system must permeate all of these areas as well.
However, the defenses are especially strong in areas that are most likely
portals of invasion, such as the skin, respiratory and intestinal tracts, and the
blood.

282. (A) The muscle tissue of the heart is known as myocardium. Layers of
epithelial tissues line this muscle on the inside (endocardium) and the
outside (epicardium). However, to ensure detachment and independence
from the rest of the components of the thoracic cavity, a sac filled with
lubricating fluid (the pericardial cavity) surrounds the heart. Lining this sac
on the outside is the pericardium.

283. (B) Plasmapheresis is the process of removing plasma from the body,
separating out protein fractions, and returning the remaining plasma
components to the blood. The proteins normally sought for removal are
those that are associated with clotting the blood to be administered to
hemophiliacs.

284. (D) On the right side of the heart, the valve between the atrium and the
ventricle is known as the tricuspid valve; that which is between the
ventricle and the pulmonary arteries is known as the pulmonary (or
pulmonary semilunar) valve. Upon reentry to the heart on the left side, the
valve between the atrium and the ventricle is the mitral (or bicuspid) valve,
and the last in sequence as the blood leaves the heart through the aorta is the
aortic (or aortic semilunar) valve.

285. (E) SRS-A (slow-reacting substance of anaphylaxis) produces a

systemic response, but as the name implies, it does so slowly and causes
sustained bronchoconstriction. Histamine, on the other hand, produces all of
the effects listed.

286. (D) The immune response is best mounted when a foreign antigen is
processed within the cytosol of a cell and then presented to a lymphocyte by
the antigen-presenting cell. This commonly occurs in the spleen.

287. (B) Systole, when the blood pressure is at its highest, is when both
ventricles are contracting with coordinated force, pushing blood out of the
heart into the lungs and tissues simultaneously. Diastole is when the blood
is not being pressurized by the heart.

288. (C) Cells differentiate early during hematopoiesis in the bone marrow
into myeloid and lymphoid cell lines. The best choice is answer C, because
a monocyte in the blood becomes a macrophage when it enters the tissues.

289. (A) Cells from a person with sickle-cell anemia fold in half due to a
mutation in the hemoglobin protein when the cells are not saturated with
oxygen, such as might occur following some physical exertion.

290. (C) For a virus to take over a cell, it must first attach to the target cell’s
membrane via a specific protein that acts as a receptor. If the cell lacks such
a receptor, then it is invulnerable to the entry of that virus. Humans are
protected from all bacteriophages, which target receptors found only on
bacterial surfaces and not in human blood or tissues.

291. (E) An autoimmune disorder is when the immune system attacks the
body and produces damage. Type 2 diabetes can be caused by several
things, including loss of sensitivity to or insufficient production of insulin,
but none are classed as autoimmunity.

292. (E) Granulocytes are leukocytes that are identified in differential

stained blood smears as multilobate cells filled with granules that appear as
spots. Lymphocytes are mononuclear agranulocytes.
293. (C) Platelets, also known as thrombocytes because of their role in
forming a thrombus (blood clot), are degenerate cell fragments found
throughout the blood. Heparin is an anticoagulant that leads to the
inactivation of thrombin, thus preventing effective clot formation.

294. (D) Hematopoiesis is the process of making blood, specifically the

cellular components. Other than the red blood cells, all of these cells are
leukocytes associated with some aspect of body defense. The thymus is a
primary lymphoid organ, but the T cells present migrated there during
gestation from the actual site of hematopoiesis—the bone marrow.

295. (A) During hematopoiesis, progenitor lymphocytes undergo random

gene rearrangements. This randomly rearranged DNA then codes for the
receptor that determines the antigen specificity for that individual cell,
which will be different from every other cell.

296. (C) The lymph system has no pump, and lymph moves slowly from
the tissues through the ducts, passing through lymph nodules and nodes that
provide immune surveillance by constantly searching for foreign proteins
draining from the tissues. This fluid is dumped back into the circulatory
system at the vena cava.

297. (B) The sinoatrial (SA) node acts as the pacemaker for the heart. The
electrical signal generated there passes through the atrioventricular (AV)
node, where the heart rate is coordinated and distributed. The signal is then
passed through the bundle of His (also known as the AV bundle) to the
Purkinje fibers, where the nerves distribute the signals to the muscle tissue.

298. (B) When the letter C is followed by a number in referring to the

blood, it indicates the protein components of the complement cascade,
identified as C1 through C9. The primary function of complement is the
targeting and lysis of invading cells such as bacteria. This means that the
lack of C4, one of the key proteins in the cascade, would prevent the lysis
and destruction of bacteria that produce an infection.

299. (B) The heart is one of the major consumers of both oxygen and
glucose because of the huge energy expense required for constant repetitive
muscle contraction. The blood providing essential materials for its function
is skimmed off the top through the coronary arteries as it exits the heart
through the ascending aorta.

300. (A) Most antigens are initially processed in the cytosol of assisting
cells that degrade the antigenic molecules into smaller fragments that are
then mounted on MHC class II surface molecules for presentation to B
cells. These presented antigens greatly amplify the antigenic signal and
increase the strength and duration of the immune response. The best
antigen-presenting cell is the macrophage.

301. (D) The cell-mediated response consists in the proliferation of effector

T cells that respond to endogenous antigens presented on MHC class I
molecules. This mechanism usually targets cancer cells and cells infected
with intracellular parasites and viruses by cytotoxic T lymphocytes.

302. (E) Assays that require free uncoagulated cells include a complete
blood count, hematocrit, and a differential stain. Measuring complement
proteins can be done on either plasma or serum. However, you could not
measure clotting time on blood collected in a material that would prevent
clotting.

303. (E) The primary antibody type of respiratory and intestinal secretions
is manufactured just inside the epithelial layer of these tissues. The IgA
antibodies are then attached to a special protein called a secretory
component that escorts them through the epithelial cells and into the mucus,
where they neutralize invaders before they have a chance to get inside the
body.

304. (D) As people age, their tissues lose flexibility, including the cells that
line all blood vessels, decreasing the body’s ability to regulate blood
pressure properly. Elevated high-density lipoprotein (HDL) levels are
associated with improved cardiovascular health and improved blood
pressure control.

305. (C) The primary immune response occurs following a first-time

exposure to an antigen and is characterized by low levels of IgM
production. The secondary response is characterized by a higher production
of IgG and the subsequent production of memory cells. The specific antigen
doesn’t seem to matter; only the level and duration of exposure determines
which response will be observed.

306. (D) Every person is born with a nonspecific immune system already in
place to serve as a low level of protection until the specific immune system
fully develops after birth. Memory cells are generated by lymphocytes only
following a specific secondary immune response.

307. (A) In an atopic person with allergies, a bee sting will precipitate a
wide-scale release of massive amounts of histamine, which opens all blood
vessels, causing fluid to leak out of the circulatory system into the tissues
and bringing on hypovolemic shock. The cells in the tissues that are filled
with histamine and covered with IgE are known as mast cells.

308. (E) Normally, basophils are observed at the lowest levels with about 1
percent or less of all leukocytes. Second fewest are the eosinophils at
roughly 3 percent. Monocytes normally come in at about 10 percent and
lymphocytes at about 25 percent. Neutrophils account for the remainder of
leukocytes in circulation.

309. (B) When the first Rh+ child is born to a mother who is Rh−, the
child’s blood acts to immunize her against that blood antigen and she will
start to produce antibodies against the Rh factor. If a subsequent child is
conceived who is Rh+, then the mother’s antibodies will cross the placenta
and destroy the child’s red blood cells, a condition known as
erythroblastosis fetalis.

310. (A) Blood clot formation is produced by the conversion of two major
factors present in the blood in inactive form. These factors are prothrombin
and fibrinogen. In essence, inactive prothrombin becomes active thrombin,
and active thrombin serves to convert inactive fibrinogen into active fibrin.
Fibrin then begins to form cross-links and produces an expanding clot.

Chapter 9: The Digestive and Excretory Systems

311. (C) The teeth in front are incisors. Behind these knifelike teeth are
those that can penetrate and hold the food in place, serving like forks; these
are called canines. Next are the teeth designed to grind and crumble—first
the premolars, and then the molars.

312. (D) Blood is circulated through the kidneys, where it is filtered to

remove waste materials for disposal in the form of urine. The urine passes
from the kidneys through ureters that connect to the urinary bladder. There
the urine pools until ready for discharge through the urethra. While the
adrenals rest on the kidneys, they are part of the endocrine system and
secrete hormones.

313. (D) Although nutrients essential for blood formation such as iron and
vitamin B12 are absorbed in the intestinal tract, all blood cells are
manufactured within the bone marrow.

314. (A) Two rings of muscle tissue, known as sphincters, surround the
urethra just inferior to the bladder. One of these is made of smooth muscle
and is under autonomic control. The other is composed of skeletal muscle
and is under voluntary control. There is no sphincter surrounding either
ureter, which are the tubes that connect the kidneys to the bladder.

315. (E) Specialized tools for viewing specific parts of the body are usually
identified with the Greek word for that portion of the body. Thus,
gastroscopy is the process for viewing inside the stomach with a
gastroscope, enteroscopy is the process for viewing the small intestine with
an endoscope, and colonoscopy is the process for viewing the colon with a
colonoscope.

316. (D) Lipids are valuable, energy-containing materials found in many

foods. However, their hydrophobic nature makes them difficult to process
and transport in the primarily hydrophilic human body. Lipids in foods are
absorbed through the small intestine into the lymph system for transport.

317. (B) The initial blood filtration is accomplished within the glomeruli of
the nephrons. These nephrons are located primarily in the outer cortex and
inner medulla layers of the kidneys. The processed urine passes from the
renal pyramids of the medulla and pools in the renal pelvis. From the pelvis,
the urine flows through the ureters to the bladder.
318. (C) The pancreas serves as both an endocrine gland and a digestive
organ. Pancreatic juice contains numerous enzymes associated with
increasing the breakdown of nutrients such as starch, fats, and proteins.
What pancreatic juice does not contain, however, is a cellular enzyme used
for the metabolism of monosaccharides.

319. (B) Renal failure means the kidneys are not functioning properly.
Since the kidneys are responsible for the removal of nitrogenous wastes,
their failure would result in a buildup of these materials in the blood, a
condition known as uremia. Since fluid balance is upset by kidney failure,
excess fluid retention commonly occurs, causing the swelling of the tissues
and generalized edema (swelling).

320. (E) The colon begins at the ileocecal valve, where the large and small
intestines connect. The first portion of the colon, the cecum, connects to the
appendix and leads to the ascending colon, which in turn leads to the
transverse colon and then the descending colon. The descending colon
connects to the rectum via the sigmoid colon, or flexure.

321. (D) For vitamin B12 to be absorbed properly, it must first be released
from food in the duodenum and combined with intrinsic factor, which is
produced in the stomach. This complex then moves through almost the
entirety of the small intestine until it nearly reaches the juncture between
the ileum and the cecum. There, it is absorbed into the circulatory system.

322. (C) The kidney on a gross scale is composed of the outer cortex, the
middle medulla, and the inner pelvis. While the reabsorption tubules
constitute most of the medulla, the filtration portions of the nephrons are
located in the cortex.

323. (D) The liver synthesizes bile and enzymes associated with digestion,
produces vital blood proteins, and stores more than 50 percent of the body’s
supply of vitamin B12 and iron. Blood, filled with substances absorbed in
the small intestines, passes through the liver before entering general
circulation. The liver participates in metabolism by the production of
glucose from glycogen and assists in lipid metabolism.
324. (E) While the kidneys do need to get rid of the excess nitrogen
associated with protein breakdown, they do not have to worry about wastes
from protein synthesis, as there are none.

325. (B) The gallbladder is a storage organ connected to the liver, which
synthesizes the digestion-aiding bile, and the duodenum, where the bile is
released after lipids are detected exiting the stomach. Since the flow of
material is one-way from liver to gallbladder to duodenum, when a
gallstone is passed, it can only go into the duodenum.

326. (D) Amylase is an enzyme that breaks down amylose, also known as
starch, into smaller sugars and monosaccharides, primarily glucose.
Digestive materials such as enzymes are produced within glands like those
found in the mouth and liver, where enzymes are stored in the gallbladder
for release into the duodenum.

327. (A) Once material passes from the blood, it is collected as a filtrate
within the Bowman’s capsule. This filtrate passes through the proximal
tubule, down the descending tubule, around the loop of Henle, and back up
through the ascending tubule. The newly formed urine is then routed out of
the nephron through the distal tubule into the collecting duct.

328. (B) Hydrochloric acid is secreted in the stomach, not the liver.
Glycogen is stored in the liver, where it can be broken down into glucose
and released into the blood. Nitrogenous wastes are removed in the kidneys
and disposed of in the urine.

329. (A) Reverse osmosis does not occur in the kidneys. Because of the
need to maintain proper fluid balance by selective retention of various ions,
not all of the process is passive. Ion flow is in both directions, while the
terms secretion and tension imply only one direction.

330. (C) Parietal cells produce intrinsic factor and HCl. Intrinsic factor is
required for the absorption of vitamin B12 at the ileocecal junction. HCl
denatures proteins and, by doing so, also kills most of the microorganisms
ingested with food. It also converts the inactive pepsinogen into active
pepsin. Mucus is produced by neck cells within the gastric pits.
331. (E) The saliva is produced by three, not four, pairs of glands. The
pharyngeal tonsils, also known as adenoids, while located in the same
general area as the glands responsible for saliva, are part of the immune
system and responsible for immune surveillance of the oropharyngeal
mucosa.

332. (C) While the autonomic nervous system does make continual use of
ions, this flow is referred to as an action potential, which eliminates answer
D as a choice. Lipids are uncharged and thus hydrophobic, eliminating
answer B as well. Proteins can be detected in the urine, providing evidence
of kidney damage, but this is done by either a dipstick screening test that
requires no current or by electrophoresis (not countercurrent), eliminating
answer A. The production of HCl within the parietal cells of the stomach is
accomplished by ion flow conducted with a sodium-potassium pump
powered by ATP; this eliminates answer E. The mechanism identified in the
question is used to describe ion flow and the control of urine concentration,
which corresponds to answer C.

333. (A) Closure of the esophagus would prevent the food from reaching
the stomach. The arrival of saliva, which moistens the food and prepares it
for a smooth trip down the esophagus, must occur prior to swallowing.
While the remaining options are all part of the swallowing reflex, the first
to occur is the sealing of the nasal passages.

334. (B) Proteins and blood cells never pass through the glomerular filter
and stay in the blood. Ninety-nine percent of the water is recovered.
Glucose, amino acids, and carbonate are all 100 percent recovered within
the proximal convoluted tubule. Both sodium and chlorine ions are
recovered in the ascending tubule with about 65 percent efficiency.

335. (E) The primary function of the small intestine is to extract and absorb
as many nutrients as possible from food. The small intestine is composed of
three sections (in order from the stomach): duodenum, jejunum, and ileum.
Digestion starts as soon as the food enters the first of these sections.

336. (A) Food enters the stomach through the cardiac sphincter. The surface
of the stomach is rugose to increase the churning mechanism. The gastric
pits secrete mucus to protect the stomach lining, but any antibodies are
denatured immediately. A peptic or gastric ulcer may develop in the
stomach, but duodenal ulcers appear in the duodenum of the small intestine.

337. (B) The retention or shedding of water in the urine is controlled by

antidiuretic hormone (ADH) secreted by the adrenals. When the body
becomes dehydrated, ADH is secreted to retain more water, which increases
the waste concentration in the urine. Ethyl alcohol interferes with the
function of ADH, thereby increasing urinary output in spite of the
dehydration condition.

338. (C) Bile is a substance that contains cholesterol, bile salts for
emulsifying lipids in foods, and other digestive enzymes. While the
gallbladder contains bile, it is actually manufactured in the liver.

339. (B) Increasing water intake increases fluid levels within the blood.
This, in turn, decreases ion concentration. When low ion concentrations are
detected by the hypothalamus, it signals the pituitary to signal the adrenals
to reduce their output of ADH, thereby increasing urinary output and
restoring fluid balance.

340. (D) The sugar levels are highest in the epithelial cells and lower in
both the intestinal lumen and capillaries. Sugars within the intestinal lumen
are at low levels and are valuable enough that the epithelial cells are willing
to expend energy to import them by active transport. Because of the size of
the molecules, they are moved into the tissues by passive carrier mediation,
and then into the capillaries by simple diffusion.

341. (E) Lipid droplets are first emulsified by bile salts in the duodenum.
These smaller droplets can then be penetrated by the lipases from the
pancreatic juices and broken down primarily into triglycerides. The
triglycerides are then packaged with proteins to form chylomicrons, which
are then transported to the lymph by epithelial cells.

342. (A) The nephron consists of the glomerulus; Bowman’s capsule; and
conducting and reabsorption tubules in the order of proximal convoluted
tubule, descending tubule, loop of Henle, ascending tubule, distal
convoluted tubule, and collecting duct. The blood enters the glomerulus via
the afferent arteriole where it is filtered. The Bowman’s capsule contains all
the components involved in filtration.

343. (C) For nutrients to enter the body, the interface between the intestinal
lumen and the tissues inside the body must be thin, not thick like the
epithelium of the skin. This inner epithelial surface is the mucosa. It is
found on the thicker submucosa, which is surrounded by the multiple
smooth muscle layers of the muscularis, wrapped within the protecting
serosa, and held in place within the abdominal cavity by the mesentery.

344. (D) The only thing listed for which the kidneys are not responsible is
the disposal of bilirubin from the breakdown of hemoglobin from recycled
red blood cells, which is disposed of in the bile and then dumped into the
feces.

Chapter 10: The Muscle and Skeletal Systems

345. (D) Smooth muscle is located throughout the body. Smooth muscle
cells are nonstriated (that’s why they are called smooth). Skeletal muscles
are associated with the bony structures of the skeleton. All smooth muscle
tissue is under the involuntary control of the autonomic nervous system.

346. (C) The adult human skull is composed of 22 bones. The braincase
bones include the ethmoid, the frontal, the occipital, two parietals, the
sphenoid, and two temporals. The facial bones include the volmer, the
inferior nasal concha, two nasal, two maxillae, the mandible, the palatine,
two zygomatics, and the lacrimal.

347. (A) Answers B, C, and E represent muscle pairs that pull in opposite
directions. Answer D represent muscles on entirely separate limbs.

348. (B) The vertebrae, or bones of the spine, provide support for the
remainder of the skeletal structure and protection for the spinal cord.
Starting just below the skull, there are seven cervical vertebrae (identified
as C1 through C7), 12 thoracic vertebrae (T1 through T12), five lumbar
vertebrae (L1 through L5), the five fused bones of the sacrum, and then the
three to five fused bones of the coccyx.
349. (A) A joint is defined as a joining between bones. Articulated joints
are held in position by ligaments that restrict their range of motion. Certain
joints, however, are not intended to be mobile, such as the sutures of the
skull. These nonmobile joints are identified as fibrous joints.

350. (E) A sarcomere is the basic contractile unit of the muscle cell and is
identified under a microscope as the region of bands located between the Z
lines.

351. (B) One of the primary functions of the bones is to serve as a reservoir
for calcium and phosphate vital for organ and cellular function. Long bones
are also home to the tissues that produce blood cells. The skeleton protects
the internal organs from trauma and provides the support necessary for
motion produced by muscle contraction.

352. (B) The sarcoplasmic reticulum serves as a storehouse of calcium ions

(Ca2+), a flood of which is necessary to initiate actin-myosin interactions
that produce muscle contractions.

353. (D) A long bone consists of three broad sections: the two ends, or
epiphyses, and the diaphysis in between. The end closest to the head is the
proximal epiphysis, and the end furthest away is the distal epiphysis. While
loss of calcium can lead to osteoporosis, this is an abnormal condition
affecting the compact bone and is not related to the normal spongy bone of
the epiphyses.

354. (C) The knee is a hinge joint articulation located between the femur of
the upper leg and the tibia and fibula of the lower leg. The tibial layer
consists of two disk-shaped cushions known as the lateral and medial
menisci. They are composed of fibrocartilage, not fibrous joining as seen in
the skull.

355. (B) Muscle contraction requires a huge energy expense. The initial
supply of ATP on hand is consumed within the first 10 seconds of
contraction. After that, the ATP is replenished by the donation of the
phosphate group attached to creatine phosphate to recharge ADP to ATP,
which lasts about an additional 30 seconds.
356. (E) Intact compact bone holds two types of cells: osteoplasts, which
are free roving, and osteocytes, which are bone cells locked in spaces
known as lacuna and connected by canalicula. Osteoclasts become active
within compact bone following a fracture, when they are needed to recycle
bone debris. These osteoclasts normally reside in the periosteum.

357. (D) Digestion is under autonomic control. The autonomic nervous

system is regulated partially by the brain stem and partially by the spinal
cord. The control of peristalsis falls to both branches of the autonomic
system, both the sympathetic and parasympathetic systems. So, although
answers A and C are true, answer D is more complete and is the correct
answer. Neither answers B nor E are involved in the involuntary system.

358. (C) During childhood, spongy bone starts to form at some secondary
ossification sites near the ends of the bones. Later, during early
adolescence, bone elongation takes place as new cartilage is laid down on
the undersurface of the cartilage growth plate, also known as the epiphyseal
plate.

359. (E) Joints are held together by collagenous ligaments. This eliminates
answer D, which does not describe a tendon, although both are composed of
collagen, and answer B as well. Answer C is incorrect because neither of
these tissues have an extensive blood supply. Answer A describes a
synovium sealed within a fibrous joint capsule. A tendon connects bone to
muscle, as in answer E.

360. (C) When an action potential signals the need for muscle contraction,
it causes a release of calcium ions from the sarcoplasmic reticulum. This
calcium interacts with troponin, opening up the myosin binding sites on the
tropomyosin strands that cover the thick filament composed of actin. This
allows the myosin heads extending from the thin filament to bind to these
sites.

361. (C) Neither rheumatoid arthritis nor osteoarthritis affect ligaments.

Both can result in permanent deformation. Osteoarthritis is most commonly
initiated by a gradual erosion of the intra-articular cartilage until bone starts
to grind on bone, while rheumatoid arthritis is initiated by an inflammatory
process classified as an autoimmune response.
362. (D) When a myofibril contracts, it is responding to a sudden release of
calcium ions from the sarcoplasmic reticulum that then permits the
expenditure of ATP to activate the sliding filament mechanism that
produces muscle contraction. The ions dumped in one cell rapidly pass to
adjacent cells through the connecting gap junctions, producing a
synchronized beating.

363. (E) When a bone fractures, blood flows out of the vessels in the
Haversian canals and produces a clot, or hematoma, that fills the fractured
area. A fibrocartilage superstructure is then formed between the bone ends
to immobilize them within the resulting callus. Osteoclasts start dissolving
the damaged crystalline structure for recycling. Following behind their
hollow trail are osteoblasts that deposit fresh, reformed bone.

364. (C) The spaces between the ribs are known as intercostal spaces;
intervertebral space is filled by the intervertebral disks between the
vertebrae.

365. (A) Tendons attach to bones that are relatively immobile at points
known as origins and attach to bones that are designed to move when the
muscle contracts at points called insertions. This means that insertions are
pulled toward origins.

366. (E) The skeleton is divided into two parts: the axial skeleton that runs
along the mid-line from the skull to the coccyx and includes the rib cage,
and the appendicular skeleton that rests on the axial. If a bone is not within
the midline, then it is part of the appendicular portion.

367. (A) After about 45 seconds of exertion, glucose must be released from
glycogen stores in the liver to fuel additional muscle contraction. If there
are no glycogen stores, such as in McArdle disease, then the muscles lose
their ability to contract after little effort.

368. (B) The tibia and fibula are the two bones that stand parallel to each
other in the lower leg, running between the knee and the tarsal bones of the
foot. Analogous to these are the radius and ulna, the two bones that stand
parallel to each other in the lower arm, running from the elbow to the carpal
bones of the hand.
369. (D) Osteoporosis is a condition brought on by calcium depletion
within the compact bone. Trying to increase calcium blood levels is a
reasonable way to try to replenish bone mass caused by calcium loss.
Moderate exercise or stretching to slightly increase stress, and thus bone
strength, in response is also a common approach to treating this condition.

370. (A) The latissimus dorsi contract to draw the arms backward and down
toward the body. The glutei maximi extend the thighs and rotates them
laterally. The external obliques rotate the trunk and squeeze the abdomen.
The serratus anterior muscles draw the shoulder blades forward and help
raise the arms. The rectus abdominis is the muscle group used for bending
the spine forward as in a sit-up.

Chapter 11: The Respiratory System

371. (B) Interspersed across the alveolar surface are septal cells that secrete
surfactants. These substances are necessary in the extremely small alveolar
sacs, because the water protecting the cell surfaces from dehydration would
cause the sacs to collapse due to its cohesive power. Surfactants reduce this
effect and permit the alveoli to remain inflated.

372. (A) Since the last stop for inspired air is within the alveoli just before
the oxygen enters the blood supply, they must be in the last position of the
sequence; this eliminates answers B and E. Similarly, the first structure
encountered as air enters the respiratory system is the pharynx, which
eliminates answer D. The larynx is superior to the trachea, which eliminates
answer C and confirms answer A as the correct sequence.

373. (D) Quiet breathing is when both the diaphragm and the rib cage
provide gentle inspiratory force. Deep breathing is what typically occurs
during more active periods. Forced breathing adds additional inspiratory
force and active muscle participation in exhalations. Shallow breathing is
the method pregnant women use due to decreased thoracic cavity volume.

374. (C) When a person is at rest, the amount of air in the lungs is called the
resting tidal volume (TV). If as much air as possible is forced out by
muscles, the quantity leaving is called the expiratory reserve volume (ERV).
The amount of air remaining in the lungs after expelling the ERV is called
the residual volume. The inspiratory reserve volume (IRV) is the maximum
amount of air a person can inhale.

375. (E) Particulates must pass through the nasal turbinates lined with
mucus. The upper respiratory system is coated with mucus that tends to trap
most of those cells that make it past the nose. This mucus moves upward for
removal from the respiratory tract; the movement is conducted by ciliated
cells. In case anything makes it as far as the alveoli, roving macrophages
are prepared to engulf and destroy the invaders.

376. (C) If you close your mouth and nose and attempt to expand your chest
using the intercostal muscles, the expanded volume without increase in air
content causes a reduction in the pressure in the lungs. That reduced
pressure is inversely proportional to the expanded volume. It is this reduced
pressure in the lungs that allows the air to flow from the atmosphere into
the alveoli. This is Boyle’s law.

377. (E) If the respiratory tubes were not reinforced with inflexible material
such as thick fibrous material and cartilage, they would collapse when the
pressure dropped and balloon out when the pressure rose. The greatest
pressure changes occur in the upper regions where the greatest pressure
variations occur. This means that the pharynx, trachea, and bronchi all
contain cartilage and the very small bronchioles do not.

378. (B) The CO2 generated in the tissues comes from the metabolism of
glucose, in which each of the six carbon atoms are used to produce this low
energy–containing waste gas.

379. (B) The cerebellum, the regulator of many involuntary activities,

mostly controls coordination and body motion. The medulla oblongata
helps control breathing.

380. (D) IgM is an antibody type that can be found in low levels in
respiratory secretions but nowhere near the high levels found in IgA. This is
because IgA is synthesized with a special secretory component that
conducts it directly through respiratory epithelial cells and into the mucus.
381. (A) Carbon dioxide presents at a higher concentration in the tissues
than in the blood, so it enters the blood by passive diffusion. There, 7
percent of it enters and remains in the blood plasma. The remaining 93
percent enters the red blood cells: about 23 percent binds to hemoglobin
and the remaining 70 percent is converted to carbonic acid (H2CO3) by the
enzyme carbonic anhydrase.

382. (E) Pneumonia is a fluid infiltration into the alveoli that interferes with
gas exchange; the most common cause of pneumonia is bacteria. Fluid
infiltration can also be caused by some chemical damage. Emphysema is a
condition in which the alveoli lose structural integrity. While lung cancer
can impair breathing, this is normally caused by a loss of access to the
alveoli due to blockages.

383. (A) Nitrogen is not biologically available as an atmospheric gas, which

means it is inert to humans. It moves freely into the blood and tissues until
it reaches equilibrium with the atmosphere.

384. (E) When the body is under considerable exertion, it requires increased
gas exchange in the lungs that is best accomplished partly by increasing the
respiration rate and partly by increasing lung volume. To accomplish both,
multiple muscles assist in expanding and contracting the rib cage (internal
and external intercostals) as well as expanding the abdomen (diaphragm).

385. (A) Cells that line the respiratory passages have cilia that beat
constantly to move material along; this keeps the passages clean and keeps
mucus from accumulating in the lungs. The goal is to get the mucus into
position where it can either be removed from the body by expectoration
(spitting) or swallowed and destroyed in the acidic environment of the
stomach.

386. (A) Within the alveolar capillaries (where the air is not quite
completely mixed with the atmosphere), pO2 = 100 mm and pCO2 = 40
mm. Within the tissues, pO2 = 40 mm and pCO2 = 45 mm. This is why O2
can passively diffuse from the blood into the tissues and why CO2 leaves
the tissues and enters the blood.
387. (E) There are two lungs in the human thoracic cavity, one on the right
side of the heart and one on the left. The right lung is composed of three
separate lobes, and the left is composed of two. The lungs are surrounded
by the pleural membranes that prevent the lungs from adhering to any
surrounding tissues. Separating the thoracic cavity from the abdominal
cavity below is the diaphragm on which the heart and lungs rest.

388. (D) Several conditions can result in elevated CO2 levels in the alveoli.
If the body is at rest and relaxed, a yawn reflex greatly increases the air
flow into the lungs and the smooth muscles surrounding the bronchi will
relax and permit bronchodilation to ease its passage. If the body is active,
the respiration rate increases, which also results in greater movement of
gasses into and out of the alveoli. However, both of these situations will
prevent a drop-off in pO2 levels.

389. (B) The receptors responsible for the cough reflex reside in areas
where such stimuli would be the result of something unexpected or unusual.
The oropharynx is the obvious area listed in which such receptors would be
counterproductive. This is because the chewing and swallowing of food
would trigger the reflex at every meal, preventing the intake of nutrition.

390. (E) COPD represents a serious condition, as impaired gas exchange

means decreased oxygenation of peripheral tissues. Answers A, B, and D
can immediately be excluded, as they all are chronic respiratory conditions.
With emphysema (answer C), the integrity of the alveolar sacs is
compromised, which greatly reduces the lung surface areas available for gas
exchange. This deterioration is usually gradual and irreversible.

391. (C) Since the air is commonly dry, the mucus membranes in the nose
increase the moisture content of the air to prevent the desiccation of the
alveoli and recover those fluids as the air departs again. The convoluted
passages in the nose also produce a cyclonic effect that spins debris onto the
mucus-coated surfaces for easy removal from the body. An additional
benefit is that the olfactory receptors within the nose help steer humans
away from potentially dangerous putrid or toxic locations or toward a
favorite food source.
Chapter 12: The Skin
392. (B) The sense of touch can actually be broken down into separate
categories of perception, and the skin is covered with neuron receptors with
different capabilities. These receptors include the capability to detect
temperatures, both heat and cold; light touches; a continued firmer touch,
and excessive touch. We can determine that our skin is being stretched
based on a composite of assorted other receptors, but there is none for
stretching alone.

393. (B) The outermost layer of the skin is composed of layers of

overlapping keratinized epithelium. Because these cells are composed of
the same proteins as horns and nails, they are described as cornified. The
lowest level of the skin is called the hypodermis (or subdermis). On this
layer rests the dermis itself, then the basal stratum of the epidermis, then the
cornified stratum already mentioned.

394. (C) An adenoma is an abnormal collection of glandular-derived cells

that is also non-cancerous. Of the remaining choices, basal cell carcinoma is
the most common type of skin cancer diagnosed but is the least dangerous.
Squamous cell carcinoma is a bit less common and more dangerous, but
only about 2 percent of these tumors metastasize. By far the most life-
threatening is melanoma, which accounts for about 75 percent of skin
cancer deaths annually.

395. (A) When signaled by the hypothalamus when the body is becoming
too warm, the approximate three million eccrine glands increase their
secretion of sweat to the surface of the skin. The sweat contains lysozyme,
which acts as an antibacterial agent, and salts in a water-based solution. The
glands located primarily in the groin and axilla regions of the body are
apocrine glands, which release their secretions through the hair follicles.

396. (D) As basal columnar cells divide, they push the daughter cell—
which has a cuboidal shape—upward. After each cell division, these
cuboidal cells keep getting pushed higher and higher toward the surface of
the skin and farther away from the nutrition provided in the dermis. These
cells then undergo terminal differentiation into keratinized squamous
epithelial cells.
397. (E) If the body’s internal temperature becomes elevated, surface blood
vessels are vasodilated and sweat is released to aid in cooling. Skin nerve
endings are merely sensory, not regulatory. The spinal cord assists in
thermoregulation but does not control the thermostat. Although the pituitary
commonly executes the directions of the hypothalamus, such is not the case
here.

398. (C) Sebum serves to seal the cracks that appear between the cells of
the keratinized epithelium and has some antibacterial qualities. Sweat pours
out onto the surface of the skin, bringing with it bactericidal lysozyme and
growth-inhibiting salts. Sensory reflexes, when activated by temperature or
pain sensors in the skin, cause an immediate involuntary withdrawal of the
body part threatened by the assault.

399. (D) The first thing the body does when a deep enough breach is
produced in the skin is to form a blood clot. Inflammatory cells then
respond quickly. Fibroblasts begin to proliferate to replace damaged cells,
and macrophages enter the wound to clear away debris. Eventually, the
original structure is restored by regenerating columnar cells.

400. (A) Since IgG accounts for about 80 percent of antibodies in the blood,
it is also the predominant antibody type found in a wound.

401. (E) The outermost layer of the skin, the epidermis, is described in
answers A and D. The description given in answer C mixes both the
epidermis and other layers, so it can also be excluded. Answer B is wrong
because it describes the outer layer as having a rich blood supply when, in
fact, it does not. Answer E provides the best description.

402. (A) Arrector pili are minute smooth muscles that pull the hairs on the
skin upright so they are perpendicular to the skin surface. This reduces air
flow across the skin and helps the body conserve heat.

403. (D) Aging cells cannot divide as quickly as they once did, which slows
the healing process. The coloration of aging skin starts to appear patchy
because of a reduction in the number of pigment-containing melanocytes,
and the cells become less capable of producing interstitial connective tissue
such as collagen. This loss of cellular productivity actually decreases rather
than increases dermal elasticity.

404. (E) Eccrine and apocrine glands line the skin and provide small
amounts of ammonia, salts, and IgA-type antibodies. Lipids, which serve to
lubricate and seal the skin surface and to provide additional protection in
the form of bacterial growth-inhibiting fatty acids, also are secreted.
Although lysozyme and antibacterial enzymes can be found in sweat,
amylase—a digestive enzyme—is not.

405. (D) The greatest contributor to hair loss is simple genetics. Male-
pattern baldness shows a more complex inheritance pattern than simple
autosomal dominance but always results in a gradual depletion of the
hormone dihydrotesterone (DHT), which leads to inactive hair follicles and
loss of scalp hair.

406. (C) The pink color of the skin is caused by the presence of
hemoglobin. Melanin is the pigment produced by melanocytes that provides
the bulk of skin coloration and the primary defense against the DNA-
damaging effects of ultraviolet light. Carotene from plants is fat soluble and
imparts color to fatty tissues that provide insulation under the skin.

407. (B) Skin mechanoreceptors that sense touch, vibrations, or pressure

include Merkel disks, which are used to detect touch and pressure; Pacinian
corpuscles, which provide data on rapid vibrations and pressure; and
Meissner corpuscles, which detect texture and vibrations. However, the
latter are not associated with hair follicles. Neither of the abilities to sense
temperature nor pain are associated with free nerve endings.

408. (C) Fingernails and toenails are composed of the same material
(keratin) as the outer layers of the epithelium, not polysaccharides or
sebum. In fact, not only are nails composed of the same material as the
epithelium, but they are also constructed by the same cells.

409. (E) The skin is vital for the maintenance of many body functions. It
provides armor and active immunologic defenses for protection and
provides a physical, water-impermeable barrier for the retention of fluids
that is vital for the maintenance of homeostasis. The skin is covered with an
estimated three million–plus sensory receptors for the detection of
dangerous conditions. While the skin is active in the synthesis of vitamin D,
it is not associated with the synthesis of vitamin A.

410. (B) The line of demarcation between the epidermis and dermis is
readily observed by the presence of peaklike projections of the dermal
tissue upward into the stratum germinativium (or stratum basale) of the
epidermis. These projections, which greatly increase the contact and
adhesive surfaces between the two, are called dermal papillae.

411. (A) The skin is involved in vitamin D synthesis when exposed to

ultraviolet light. This vitamin is then transported to the liver, where it is
converted to calcidiol (and then into calcitriol in the kidneys) to help
regulate blood calcium levels and increase absorption of calcium in the
small intestine.

Chapter 13: The Reproductive System and Development

412. (C) A human sperm is a greatly reduced haploid cell. The sperm itself
is composed of a head covered with the acrosome and containing the
nucleus. While the description given in answer B may be true (although we
do not know that), we do know that answer C is true, making it the best
choice with the rest the responsibilities of other sperm components.

413. (A) Embryonic development begins only after fertilization of the

secondary oocyte by the sperm. After fertilization, the now diploid cell
divides three times without intervening growth periods, ending this
cleavage period with eight cells but with a total mass equal to the zygote.
These cells then begin growing and increasing in number as the morula
continues passing down the fallopian tube to the uterus. The final stage, the
blastocyst, is advanced enough for implantation into the uterine wall.

414. (D) During gametogenesis, the original diploid mother cell (2n)
undergoes DNA replication to become tetraploid (4n). At this point, meiosis
begins when the chromatids align and exchange DNA segments during a
process called crossing over. This cell then undergoes two consecutive
reduction divisions, first becoming two diploid cells (2n) and then
becoming four haploid cells (1n), completing meiosis and the formation of
the gametes.

415. (B) An ectopic pregnancy is one in which the blastocyst attempts

implantation at some location other than in the uterus. This attempt may be
on the peritoneal lining, ovaries, or cervix, but the most common location is
within the fallopian tube itself. Thus, it is described as a tubal pregnancy,
accounting for 95 percent of such pregnancies.

416. (E) The cells on the exterior of the blastula form the ectoderm, the
inner sphere forms the endoderm, and the connections between form the
mesoderm. The ectoderm then undergoes differentiation to form the
nervous system (including the posterior pituitary and retina of the eye), the
epidermis and tissues associated with the epidermis such as sweat glands,
the lining of the mouth, and tooth enamel. The functioning portion of the
thymus is formed from the endoderm.

417. (A) The formation of a vertebrate’s central nervous system follows the
formation of the notochord, which establishes the developmental axis of the
organism. Once the notochord has begun forming, the adjacent neural plate
forms on its ventral side. This plate then forms a furrow or groove,
invaginates further to form a fold, and then spreads its interior to form the
neural tube.

418. (D) The allantois, which includes the chorion, is a tissue associated
with the handling of liquid fetal waste and eventually gives rise to the
urinary bladder.

419. (D) In spermatogenesis, the spermatogonium divides by mitosis. Upon

division, the cell in contact with the seminiferous tubule remains to divide
again, while the one closer to the lumen (the diploid primary spermatocyte)
undergoes meiosis. It first replicates its chromosomes to become tetraploid,
then undergoes meiosis I to become two diploid secondary spermatocytes,
and then immediately undergoes meiosis II to become four spermatids.

420. (B) A woman’s reproductive age runs from the onset of menses at
about age 15 to menopause at about age 50 to 55, for a total of about 40
years. One or two eggs mature and are released every 28 days or so. This
means that about 500 total eggs become available for fertilization in her
reproductive lifetime. Estimates for the total number of eggs produced
before birth within the ovaries range from 500,000 to 1.5 million.

421. (C) Each oocyte undergoes asymmetrical cell division, so only one of
the four resulting haploid cells contains the bulk of the original cell mass
and nutrients. During the formation of the mature ovum, the primary oocyte
undergoes meiosis I to produce a secondary oocyte and one smaller polar
body. After both cells undergo meiosis II, there remains one haploid ovum
and three much smaller haploid polar bodies.

422. (D) Answer E can be eliminated because an unfertilized ovum is

incapable of further division. Answer A is also not possible because of the
change in the zygote cell membrane that occurs immediately after
fertilization. Answer B would result in genetically related but distinct
fraternal twins. Answer C has been known to occur and results in a
chimeric, or tetragametic, individual who appears normal but possesses
cells with different genetic content. Thus, D is the correct answer.

423. (A) Muscle tissues and connective tissues, including the bone marrow
from which all blood components derive, develop from the mesoderm layer,
as do the circulatory and lymph systems.

424. (B) The male reproductive system contains various tissues with
different functions. Sperm are formed in the seminiferous tubules that
comprise the bulk of the testes.

425. (A) The ovarian cycle occurs simultaneously with the uterine cycle
and consists of the follicular phase of days 1 through 14, during which FSH
levels rise and the maturing ovarian follicle containing the secondary
oocyte increases estrogen and progesterone levels, and the luteal phase
when LH levels rise—causing the release of the oocyte—and the residual
corpus luteum starts secreting progesterone.

426. (C) No significant amount of cytosol is seen in any sperm, and since it
has no other mission than to fertilize the ovum, it has no need of protein
synthesis, which eliminates the need for an endoplasmic reticulum, Golgi
apparatus, or ribosomes.
427. (C) Infant jaundice is generally caused when a mother’s naturally
forming anti—blood group antibodies cross the placenta and damage some
of the infant’s red blood cells in an ABO mismatch. This destruction
releases bilirubin which is observed as the yellowish skin and eye condition
known as jaundice.

428. (C) During very early embryonic development, three basic germ layers
form from which all future tissues and organs develop. From the endoderm
develops the bulk of the gastrointestinal system, liver, pancreas, lungs,
thymus and thyroid glands, portions of the ears and pituitary, and the
urinary bladder.

429. (E) Sertoli cells support spermatogenesis by clearing cytoplasmic

debris released during sperm maturation and secrete various substances that
work with or on testosterone. Production of the testosterone itself is the
responsibility of the seminiferous tubule interstitial cells.

430. (E) Since to the mother’s immune system the fetal tissues represent a
foreign object with distinctly different antigens, the placenta provides a
barrier that protects the fetus from maternal rejection. However, an infant is
protected for a few months after delivery by serum antibodies acquired
from the mother during gestation.

431. (E) Oxytocin is responsible for expelling the milk from the alveoli in
which it is produced. High levels of estrogen following delivery slows milk
production. A sudden drop in progesterone induces milk production
following delivery. Prolactin is responsible for regulating milk production
following birth. Testosterone has no role in lactation.

432. (B) Mammals, along with birds and reptiles, produce four
extraembryonic membranes that support fetal development: the amnion, the
allantois, the yolk sac, and the chorion. The myometrium is maternal, not
fetal, tissue and is responsible for uterine contractions during childbirth.

433. (B) During the first three weeks of gestation, the embryo first
undergoes initial tissue differentiation and then gastrulation, which results
in the formation of the three initial germ layers: ectoderm, mesoderm, and
endoderm. During the fourth week, the eyes appear, the limbs and bones
begin to form, and the heart begins to beat.

434. (D) The tissues between the fingers and toes are initially vasculated,
but these disappear at the same time as the tissues themselves. Although
answer C may present a plausible explanation, answer D is the actual
correct choice.

435. (B) Both the luteal phase of the ovarian cycle and the secretory phase
of the uterine cycle occur between days 15 and 28 of the menstrual cycle.

Chapter 14: Genetics

436. (A) Eukaryotes and prokaryotes have both genomes and genotypes. A
genotype best represents the genetic content of expressed genes, usually
focusing on individual genes and comparing their content individual to
individual. The genome represents the entire content of the nucleus (for
eukaryotes) or nucleosome (for prokaryotes) of an individual.

437. (E) Banding patterns produced with Giemsa stain after trypsin
digestion of cells arrested in metaphase reveal that there are 22 homologous
pairs and 1 nonhomologous pair (the sex chromosomes) in male nuclei.

438. (C) Klinefelter syndrome results when one of the gametes that
produced the zygote contains an extra X chromosome produced by
nondisjunction during gametogenesis.

439. (B) In the ABO blood group system, the individual’s blood group is
controlled by one set of alleles. Homozygous individuals may be blood
group A, B, or O. Heterozygous individuals may be blood groups A (AO),
B (BO), or AB. This indicates codominance.

440. (E) During meiosis, a primary diploid cell undergoes DNA replication
and becomes tetraploid. While in this state, homologous chromosomes align
tetrads and undergo intentional but random gene rearrangements in a
process known as crossing over. After this recombination, the tetraploid cell
undergoes two sequential reduction divisions, with each cell becoming
haploid.
441. (D) All of these answers represent genetic diseases. Cystic fibrosis,
however, is caused by a defect in an ion channel protein controlling sodium
transport. This results in excessive mucus secretion in the lungs, which
leads to bacterial infections and fatal pneumonia.

442. (B) Mitosis is a process in which an individual cell replicates its DNA
with high fidelity and then divides into two genetically identical daughter
cells. When a single diploid cell replicates its DNA and then divides into
four genetically distinct daughter cells, it is called meiosis.

443. (E) If both parents are heterozygous, then the four blood types will be
equally represented.

444. (A) Convention used in the construction of Punnett squares is that

dominant, codominant, or incomplete dominant alleles are indicated by
capital letters. Recessive alleles are indicated by lowercase letters.

445. (D) Gametes contain only 1 copy of each chromosome, so their genetic
content is half of the somatic cells, meaning that gametes contain a total of
only 23 chromosomes.

446. (A) Any change in a DNA sequence is a mutation, and these changes
in genotype may or may not be observed in the phenotype.

447. (B) X-linked refers to a gene whose allele is present on the X

chromosome. These genes follow the same rule of dominance as alleles
found on the autosomes except that expression may depend on whether the
alleles are expressed in male or female individuals.

448. (B) Tay-Sachs is an autosomal recessive condition. Someone with Tay-

Sachs suffers muscle degeneration because of a defect in a lipid-producing
enzyme that causes excessive lipid buildup in the CNS.

449. (C) An unmatched allele on a sex chromosome best describes a

hemizygous condition, not a locus. A gene product that affects another gene
product indicates epistasis, not a locus. While the term locus can refer to
any gene on any chromosome, it refers to the actual physical location on a
chromosome, which makes answer C the best choice.
450. (C) If one animal has brown hair and another black, then their
genotypes (and therefore genetic sequences) also differ, eliminating both
answers A and E. Additionally, because the animals differ in gene
expression, they must differ in allelic composition, also eliminating answer
D. While both animals may or may not have the same parents, they
definitely have the same brown hair because they both possess the same
dominant allele. This makes answer C a much better choice than answer B.

451. (D) Expression of genes on one chromosome can affect the expression
of genes on a different chromosome by epistasis, making answer C
incorrect. If such genes are on different chromosome pairs, then they must
be autosomal, eliminating answer A. Genes on separate chromosomes are
never linked (eliminating answer D). Although genes on separate
chromosomes might show up in the same gametes (making answer B a
possibility), they very well might not, because they always sort
independently (making answer D the best choice).

452. (B) A series of fragile chromosomes or any other genetic disorder may
result in the expression of a syndrome, but they are not the syndrome itself.
This eliminates both answers A and C. A syndrome always has some
description, so although it may be poorly defined, it is never undefined,
eliminating answer D. A syndrome may be a series of uncommon
conditions, but the word is derived from Greek roots that mean “running
together,” as in symptoms or signs that appear to run together in the course
of a certain disease process. This makes answer B the best choice.

453. (A) Evidence for mitochondrial endosymbiosis includes the fact that
mitochondria contain their own DNA, which has primarily prokaryotic
sequences (eliminating answer E). Just as a collection of bacteria in a
colony displays some heterogeneity in genetic content, so multiple
mitochondrial genomic variations are found within an individual cell. This
eliminates answer D. Mitochondria are only found in the cytosol of
eukaryotic cells (eliminating answer B) and never in a prokaryote
(eliminating answer C). Answer A is the best choice, although there is
recent evidence that some paternal mitochondria sneak in every once in a
while.
454. (C) Changes in the DNA that occur within an intron, even extensive
ones such as deletion or inversion mutations, could produce the situation
described in the question. This eliminates answers B, D, and E. A silent
mutation is one in which the coding DNA changes, but the resulting protein
is identical in amino acid sequence to the wild type. That means that answer
A can also be true and can be eliminated. What cannot be true, however, is
that this could be a neutral mutation because, by definition, it produces a
change in the protein sequence, making answer C the only correct choice.

455. (D) The purpose of the testcross is to determine whether the genotype
of an individual displaying the dominant characteristic is homozygous (say,
GG) or heterozygous (Gg). Crossing this unknown with an individual who
is known to be homozygous recessive (gg) will result in a ratio of either all
displaying the dominant characteristic, because all of the offspring of GG ×
gg will be heterozygotes (Gg), or a ratio of 1:1, because the cross of Gg ×
gg will produce 2 × Gg and 2 × gg. This makes answer D correct.

456. (E) If the daughter expresses the recessive gene, then she must be
homozygous recessive. If the gene expression is sex-linked, then it is found
only on the X chromosome. Answer A cannot be correct because it would
mean that the allele she inherited from her father was dominant, and answer
C is wrong for the same reason. Answer B is incorrect because if the mother
is heterozygous, then there is a 50:50 chance that any sisters would inherit
the dominant trait, and answer D is also incorrect as the same would be true
for any brothers. Only answer E is correct.

457. (D) While blood group AB+ is known as the universal receiver
because any individual with that blood type lacks natural antibodies that
would cause a transfusion reaction, it has not been subject to selective
pressure and offers no evolutionary advantage. Turner syndrome is the
result of a female individual having only one X chromosome. This also
offers no selective advantage, making answer C a poor choice. Down
syndrome, or trisomy 21, is the result of an individual receiving an extra
twenty-first chromosome, which confers no advantage, making answer E
another poor choice. Colorblindness, answer A, is a characteristic that
confers neither positive nor negative advantages and can also be eliminated.
The sickle-cell mutation, when present in a homozygous individual, carries
with it a high selection pressure against that person. On the other hand,
individuals who are homozygous normal are very susceptible to death by
malaria. Individuals who are heterozygous, however, are partially protected
from malaria and have a reduced chance of sickle-cell crisis because they
also carry a normal allele.

458. (B) The ABO blood group inheritance is controlled by codominance.

Thus, a person with type O blood is simply homozygous recessive and a
person with AB blood is heterozygous codominant A and B. This
eliminates both answers A and C from further consideration. Both answers
D and E are possible with simple dominance, eliminating them as well.
Answer B, however, is a classic case of codominance in which the
heterozygous condition is a blend of the dominant and recessive
characteristic.

459. (D) There are 64 codon positions in the standard genetic code. Three
of these are stop codons that carry release factors to the ribosome during
protein synthesis instead of essential amino acids. These release factors
cause the termination of translation and the release of the protein from the
ribosome. If a specific tRNA were no longer available, then the result
would be similar to a nonsense mutation that causes early termination of a
protein, but instead of being in just one protein, it would occur in all or
almost all of them. This would clearly disrupt most cellular functions.

460. (D) Meiosis produces gametes that are subject to Mendel’s laws. One
of these deals with independent assortment. Under this law, the four genes
identified would sort independently of each other. By simply multiplying
the probability of each allele times the others, we determine the number of
different possible combinations. Normally this would be 2 × 2 × 2 × 2 for a
total of 16. However, the gene identified as B is present in only one allelic
form, changing the calculation to 2 × 1 × 2 × 2 for a total of 8.

461. (C) Because genes located physically close together have a greater
chance of moving together during crossing over and thus being inherited
together, they are said to be linked. The closer the genes, the more likely
they are to move together. The centimorgan is a calculated value
representing the likelihood of genes crossing over together and is thus an
approximate value for their actual distance from each other on the
chromosome. While there are huge variations because of the wide
differences in the distribution of noncoding DNA, one centimorgan
averages to be about one million base pairs in humans.

462. (B) Epistasis is when the expression or effects of one gene is

influenced by one or more modifier genes. The mechanism may be at either
the genotypic or phenotypic level. Answer D can easily be discarded
because the effect described is a normal expression of different alleles for
the same gene. Answers A and C are unlikely, as both can be explained by
sex-linked inheritance. Although answer E may well be true, answer B
presents a much more likely scenario and is the best choice.

463. (C) Answer E describes a condition of separation, not segregation, and

can be ignored. Answer A is incorrect because the separation is not
complete; if it were, most gametes would vary from in genetic content.
Answer B is incorrect for the same reason. Answer D describes the effects
of Mendel’s second law, that of independent assortment, and is therefore
incorrect. Answer C correctly identifies the principle of Mendel’s first law.

464. (E) Hemophilia may be due to a problem with thrombocyte levels or,
more likely, a deficiency in one of the clotting proteins. This condition is of
historical note, because it has afflicted many of the royal houses of
European countries due to the frequent marriages between relatives. It was
observed that male children were much more commonly afflicted with this
life-threatening disorder than were females. This was because the women of
these families were often heterozygous for the affliction gene that was
found on the X chromosome. Since males have only one X chromosome, if
they inherited the bad gene, they were afflicted. This is a classic case of an
X-linked recessive inheritance pattern, making answer E the correct choice.

465. (A) Four gametic combinations are possible for both parents: AB, Ab,
aB, and ab. The Punnett square would reflect the 16 possible (2 × 2 × 2 × 2)
combinations. The ratios reflect the phenotypes, not genotypes. When run
in this manner, there are nine squares in the grid where both capital letters
are present, three each where two lowercase letters are coupled with at least
one capital of the other type, and one where only the recessives are present.
The resulting ratio is thus 9:3:3:1.
466. (E) Mutagenesis is defined as the process of making mutations.
Carcinogenesis is the process of making transformed cells that lead to
cancers. These definitions allow the removal of answer A. The production
of cancer cells is thought to be a two-step process: first, oncogenes are
present, and second, a mutation causes a cell to proliferate without adequate
control. This allows the simultaneous removal of both answers C and D.
Since oncogenes are present at birth but cancers do not form until after
some mutational event, this means that answer B is incorrect and answer E
is the correct choice.

467. (D) Recombination frequencies can be used to determine linkage. The

fewer recombinants after crossing, the closer the genes. The data presents
the smallest frequency as 3 percent between 1 and 3, making them the
closest together. This eliminates answer B where they are farthest apart, and
answers C and E, because both choices are not possible in either answer.
Conversely, the largest frequency is given as 25 percent between 1 and 2,
making them the farthest apart. The sequence must therefore be either 1-3-2
or 2-3-1. Only answer D correctly presents this order.

468. (D) Pleiotropy is when a single gene affects multiple other genes.
Epistasis is when the effects of one gene are modified by the influences of
several others. Hypostasis is a subset of epistasis where one gene is
suppressed by the second. Answer E would be tempting if body height were
controlled by a single gene, but it is much more complex than that and
involves the interactions of scores of different independent genes (answer
D).

469. (C) Karyotyping is a technique for observing the condition and

distribution of chromosomes in a single cell. It cannot be used to detect
mutations of specific genes for such genetic diseases as Tay-Sachs, sickle-
cell anemia, and cystic fibrosis. Since hemolytic anemia is an autoimmune
disorder, it also cannot be detected with this assay. However, the
observation of a third chromosome 21, a condition known as trisomy 21,
makes it obvious that a child is afflicted to some degree with Down
syndrome.

470. (A) Trisomy 21 identifies a condition in which a child was conceived

with a sperm or an ovum that was the result of nondisjunction during
gametogenesis. Since this condition does not present unusual antigens on
cells, they will not be targeted for destruction by apoptosis following
immune surveillance. Additionally, although trisomy 21 generally leads to
diminished mental development, it is not a fatal condition. Gene therapy, as
currently envisioned, offers the possibility of adding an effective gene to
cells that lack them but cannot be used to remove entire chromosomes.
Although trisomy 21 could be detected in every cell of a body, this is not
the case with cancers, which are clearly clones of abnormal cells. Since
transformed cancer cells lack the ability to control their own growth, these
cells evidence abnormal distributions of DNA in their nuclei, making both
cancer cells and cells with trisomy 21 aneuploidy.

471. (B) There are three alleles for the ABO blood system. Because the A
and B antigens bear a close resemblance to naturally occurring sugar
combinations in food, individuals with these blood types will develop
natural antibodies against the opposite blood type. The Rh factor is
independent of this, although low levels of anti-Rh factor will develop in
Rh− individuals. Answer A is incorrect because of the dilution effect of the
donor’s cells that would occur following transfusion. Having a protozoan
parasite present in donated blood would not produce a transfusion reaction,
although it might cause malaria later, eliminating answer E. That Jim’s
blood has some antigens is indicated by it causing a reaction, and this
eliminates answer C. Although answer D might be true, answer B is clearly
the better choice.

472. (E) This question is not asking for the expected ratio of phenotypes but
the actual distribution of genotypes. It is also important to give the
distribution after two testcrosses, not just the first. The first testcross would
result in a population that is entirely heterozygous. However, crossing
GgHh × GgHh, while resulting in a phenotype distribution of 9:3:3:1,
would also result in the appearance of nine different genotypes. Five of
these are only represented once, three are represented twice, and one—
GgHh—is expected 5 out of 16 times. This makes answer E the correct
choice.

473. (B) To categorize the chromosome distribution within a cell, it must be

observed during mitosis. To increase the likelihood of observing a full set, a
substance is added to arrest the cell cycle during this stage. The nuclei are
then squashed to disperse the chromosomes and stained with Giemsa stain
to aid in the identification of pairs by both length and banding patterns. The
substance most commonly used to arrest the cell cycle is colchicine, which
inhibits the formation of the microtubules used to separate the
chromosomes following metaphase.

474. (C) A pathogenic condition is most commonly treated at the

phenotypic level. This means that whatever physiological imbalances are
being encountered—be they infectious, genetic, or chronic—can be either
restored to normal or ameliorated by intervention. Genetic modalities can
be offered if there is a genetic basis to the disease. Answers A, B, D, and E
all represent mechanisms that intervene at the genetic level. Only answer C
presents a change after genetic expression has occurred, making it the
correct choice.

475. (A) Answers B, C, and E can immediately be removed from

consideration, because only the male contributes the Y chromosome, and
only one can normally be present in the zygote. The two possible
combinations of X chromosomes from the female are XX or 0 (representing
none present). If the male contributes an X chromosome, then the possible
results of fertilization will be XXX and X0, which does not appear as an
option. If the male contributes a Y chromosome, then the possible
combinations become XXY and Y0 which is answer A.

476. (D) Karyotyping analysis requires nucleated cells. A spinal tap not
only would entail unacceptable risks but would not be particularly efficient
for harvesting cells, so answer E is an especially poor choice. Both answers
A and C would collect mostly fully differentiated and nondividing cells and
would not prove useful for this technique. While some fetal cells can be
detected within the mother’s circulatory system, the best method for fetal
analysis is the collection of fetal cells sloughed free into the amniotic fluid
by amniocentesis, making answer D the best choice.

477. (C) Dominance is a condition in which the presence of one allele

prevents the expression of another, not reflecting any difference in
expression. Epistasis involves multiple genes, not alleles. The Hardy-
Weinberg law deals with constant gene frequencies, not variations of
expression. In genetics, leakage refers to the flow of genes horizontally or
from one species to another and has no application here. Penetrance is the
term used to describe differences between the number of individuals
carrying a gene and the number expressing the gene.

478. (A) Trisomy 21 is a congenital disorder. While it might be passed on to

progeny, inheritance is not the source of the initial problem. In utero
infection with Toxoplasma gondii, acquired by the mother from cat feces,
can produce congenital anomalies but not the distribution of chromosomes
throughout the fetus. Exposure to carcinogens after conception would only
affect patches of cells or tissues, not the genetic content of every cell in the
body. Fragile X syndrome is caused by a change in the structure of the X
chromosome, not by the addition of any. Trisomy 21 is caused by a
nondisjunction division in which one gamete receives two copies of gene
21, while its sister gamete receives none, and the former produces a
subsequent zygote.

Chapter 15: Evolution

479. (A) Monoecious is a term used by botanists to describe a single plant
that has both male and female gonads. Using it in reference to humans
would therefore be incorrect, so answer D is out. Selection is a process
rather than a difference, so answer E can also be ignored. Polymorphism
means “many shapes” but is used in biology to describe phenotypic
variations that lead to diversity, not differences in sexual morphology,
making answer C a poor choice. Males and females may have features that
distinguish them from the other sex (answer B), but the presence of
distinction within a population is referred to as sexual dimorphism, making
answer A correct.

480. (B) While the Hardy-Weinberg law may be used to understand the
distribution of alleles in a population such as the one described in the
question, it cannot be used to describe the situation itself. A genetic
bottleneck is when some event reduces a population to a relatively low
number of reproducing individuals. While this term may be used to describe
what might happen to the species in the question, it is not accurate in
describing the situation itself. Once the population became established, it
would start to experience drift as mutations occurred and the population
became more diverse; it might even experience disruptive selection if the
selection pressures established two different populations from the extremes
of some characteristic, but neither of these fit the description in the
question. That description presents a situation where the founder effect
would be at play.

481. (C) The standard levels of this taxonomic hierarchy can be

remembered with the mnemonic “King David (Phillip) Came Over For
Good Steak” where each initial letter stands for a level. The most recent,
highest, most inclusive categories are superkingdoms or domains, followed
in order of greater specificity by kingdom, division (or phylum), class,
order, family, genus, and species. The term binomial refers to the latter two
categories, which are minimumly and most commonly used to identify a
species. The most inclusive category of the answers presented is phylum;
all of the others are subcategories of it.

482. (E) The early atmosphere is thought to have been constituted by gasses
given off by the extensive volcanic activity envisioned when the earth was
new. Because these gasses are detected in volcanic outgassing today, they
include carbon dioxide (answer A), hydrogen sulfide (option B), sulfur
dioxide (answer C), and nitrogen (answer D). Oxygen (answer E) is not
included on this primitive list because it is thought that molecular oxygen
was generated primarily through organic processes, meaning that life had to
be around a while before the gas could be generated in sufficient quantities
to help form the atmosphere.

483. (D) Evidence that supports the endosymbiotic theory includes the
following: these organelles have their own independently replicating
genome that is bacterial in structure; they grow and divide by binary
fission; they have their own form of genetic code used for translation in
bacterial-type ribosomes; and they are both enclosed in a double membrane,
such as would be the case if they had entered by invagination of the host
cell membrane.

484. (D) Alleles are variations of genes that appear at the same genetic
locus, and they result in changes of phenotypes within a population.
Migration and random mating are best associated with the descriptions of
populations, not changes at the DNA level. Independent assortment refers
to the distribution of different genes at different loci, not alleles at the same
locus. Errors in meiosis might include nondisjunction or unequal exchange
of DNA segments during crossing over, but these are almost always
detrimental and do not lead to speciation. Mutations, on the other hand, can
produce small, incremental changes within genes, producing allelic
variations that can lead to speciation.

485. (C) For carbon 14 to be detectable, it must have been introduced into
the earth’s atmosphere recently. In fact, it is generated at an apparently
constant rate in the upper atmosphere by high-energy cosmic rays. Once
present, it is incorporated at the same rate as regular carbon 12 into plant
material during the Calvin-Benson cycle. The ratio of carbon 12 to carbon
14 remains constant until the carbon fixation process is interrupted by the
death of the plant. At that point, the carbon 14 level starts to decrease and
continues to do so as the plant material is ingested and the radioactive
carbon is incorporated into the tissues of consumers. The carbon 12 to
carbon 14 ratio can be used to date organic materials up to about 10 half-
lives, or to about 50,000 to 60,000 years ago.

486. (A) This question really focuses on exactly what the theory of acquired
inheritance is. It is simply another name for Lamarckian inheritance. Jean-
Baptiste Lamarck preceded Charles Darwin and proposed the idea that
organisms can pass on phenotypic characteristics they develop during their
lifetime to their progeny. An example of this is a bulky weight lifter passing
on his muscle mass to his children. This theory was replaced once Darwin’s
theory of natural selection was proposed. The statements presented in
answers B, C, D, and E support Darwin’s, not Lamarck’s, theory.

487. (B) Alexander Oparin hypothesized that simple organic materials, such
as those that may have been used in the development of the first life on
earth, might have spontaneously formed under the natural conditions
thought to be present at the beginning. Stanley Miller and Harold Urey
tested the idea by placing methane, hydrogen, water, and ammonia in a
sealed system through which electrical currents (simulating lightning)
passed. At the end of the experiment, analysis revealed that more than 11
amino acids, as well as simple sugars and organic acids, had been formed
under these abiotic conditions. No nucleotides, DNA, or lipids were
observed.
488. (C) The calculations associated with the Hardy-Weinberg law are
based on seven assumptions: mutations within the population are not
appearing; natural selection is not occurring; all members of the population
will breed; mating is totally random, and there is no sexual selection; the
population is infinitely large; there is neither immigration into nor
emigration out of the population; and offspring of the population members
is evenly distributed.

489. (E) Populations are subject to variations in selection pressures, which

is why biodiversity is so vital. Within any population, there commonly
exists a normal distribution of allelic variations. Three basic forms of
selection pressures can affect this distribution: directional selection,
disruptive selection, and stabilizing selection. Directional selection tends to
remove one of the extremes in variations, which results in a shift of the
average within the population toward the other extreme. Disruptive
selection puts pressure on the mean for the population, increasing the
relative numbers in the extreme. The last is stabilizing pressure where the
extremes are culled, narrowing the distribution of the alleles around the
mean.

490. (A) Adaptive radiation (meaning “in all directions”) is a mechanism by

which several allelic variations begin to appear within a population, each of
which will eventually develop into separate species. The founder effect is
produced by a sudden geographic isolation. There are thought to be four
basic types of speciation: peripatric, parapatric, allopatric, and sympatric.
Peripatric is speciation in which a small group at the periphery of the larger
population begins to separate. Parapatric is when one large population
begins to form two separate but adjacent species. Allopatric is speciation
resulting from geographic isolation. Sympatric is when a single population
within the same geographic area begins to diverge based on some allelic or
behavioral difference.

491. (B) Three of these answers can immediately be eliminated from

consideration. Even within a single species, we find variations in fitness, all
organisms survive best within a relatively narrow range of environmental
factors, and we often find the same gene sequences in organisms ranging
from amoebas to humans. The very definition of a population is members of
the same species within the same area, all of which have identical resource
requirements. Since organisms must maintain homeostasis to survive, and
maintenance of homeostasis requires the ability to respond suitably when
the surrounding environment changes, answer B would only lead to
extinction and is the correct choice.

492. (E) In the beginning, there were no organic materials, and formation of
any complex compounds had to occur under abiotic conditions.
Experiments have shown that both amino acids (and thus proteins) and
lipids—which have the ability to spontaneously form lipid bilayers—can be
produced under these initial abiotic conditions. This makes them likely
candidates to be the next in the chain toward life and removes them as
likely choices. Nucleic acids appear to require biologic precursors, and
RNA is thought to have appeared first, because it offers the ability to
function as an enzyme in the form of the autocatalytic cleaving ribozyme.

493. (B) The concept of drift implies small, sequential changes. This
typically excludes answer D, where the term shift would be more
appropriate. The same would be true for movement of gene sequences
horizontally (removing answer A) and from species to species (removing
answer D). Genetic drift refers to changes within DNA and does not involve
great distances (removing answer C). The remaining answer, B, correctly
describes genetic drift.

494. (D) It is thought that the earliest forms of life arose under conditions
that we would consider extremely hazardous to most life-forms today. This
implies that organisms that continue to live in these extreme environments
most closely resemble their early forebears. This immediately eliminates
answer A, which is a complex eukaryote. Of the three prokaryotes
remaining, answers B and E are considered much more advanced than those
of the weird and primitive Archaea domain. While a bacteriophage is even
simpler than the simplest bacterium, it is much more likely that coliphages
(answer C) represent a degeneration of a live cell rather than a step toward
one.

495. (B) Many populations of organisms are geographically isolated and

considered separate species because they appear different from each other,
but they can, in fact, interbreed and produce fertile offspring. This probably
indicates that the individual populations are related to a common ancestor.
While this may have occurred following geographical isolation, it is not
necessarily so. Hybridization would require reproductive availability, not
isolation. While hybrid sterility is commonly caused by differences in
chromosomes, this is not due to aneuploidy. Although two populations
might become extinct due to selection pressures, the fact that there are two
different populations actually minimizes this possibility rather than leads to
it.

496. (A) This formula is a well-known representation of the stability of

alleles in a population under very restrictive conditions. Here p represents
the frequency of the dominant allele, and q represents the frequency of the
recessive allele. The conditions under which this formula works never exist,
as it represents an ideal state, but it can be used to provide base values
against which changes can be measured. This formula is known as the
Hardy-Weinberg equation.

497. (C) Geologic strata are commonly dated based on the fossils they
contain. These strata are classified into eons that are divided into eras and
then further divided into periods. These periods can also be further
subdivided into epochs and even shorter ages. Periods within the
Proterozoic or the older Archean eons are commonly just referred to as
Precambrian. The sequence from the oldest to the newest periods is
Cambrian, Ordovivian, Silurian, Devonian, Mississippian, Pennsylvanian,
Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary.

498. (D) A predator is defined as an organism that feeds on a host but does
not live in or on the host. This predation may or may not involve the death
of the host. A parasite feeds on a host while living in or on the host. By this
definition, a lion is an obvious predator but so are mosquitos and ticks. A
tapeworm is an obvious parasite but so is a louse. The distinction between
predator and parasite is not size, complexity, metabolism, or even the
presence of hermaphroditism. The distinction is in where the nonhost lives.

499. (E) While there are many definitions for hybrid in biology, all of
which contain the concept of mixing, when sterility is involved, the best
focus is on the progeny resulting from breeding organisms from different
taxonomic categories, most commonly separated at the species or genus
level. While such a cross can produce viable offspring, the offspring are
also commonly sterile. This sterility is not due to failure to function or to
reduced fitness, because hybrids commonly express increased—not reduced
—vigor. Failure to find an optimal place to live also will not produce
sterility. The most common cause of hybrid sterility is a mismatch in the
chromosomes, for example, a cross between a horse (with 64
chromosomes) and a donkey (with 62) results in infertile mules or hinnies
with 63 chromosomes.

500. (D) The identification of geologic strata is often based on the types of
fossils they contain. There are notable benchmark events going backward
from the present day. During the long period classified as Precambrian,
simple multicellular organisms first appear about 700 million years ago,
eukaryotes appear about 2.1 billion years ago, and the oldest prokaryotic
fossils can be found in strata dating from about 3.5 billion years ago.