Select the best answer.

1) Which of the following is a TRUE statement about viruses?

A) After assembly of the capsid, growth of virus particles continues until they are released.

B) A virus particle contains both DNA and RNA.

C) Individual virus particles are visible with light microscopes.

D) Viruses are classified below the cellular level of biological organization.

E) Assembly of viral capsids from proteins requires host cell assistance.

 
 

2) Transcription of the structural genes in an inducible operon

A) does not produce enzymes.

B) occurs all the time.

C) starts when the pathway's product is present.

D) starts when the pathway's substrate is present.

E) stops when the pathway's product is present.

 
 

3) Which of the following represents a difference between viruses and viroids?

A) Viruses have capsids composed of protein, while viroids have no capsids.

B) Viruses contain introns; viroids have only exons.

C) Viruses have genomes composed of DNA; while viroids have genomes composed of RNA.

D) Viruses cannot pass through plasmodesmata; viroids can.

E) Viruses infect many types of cells, while viroids infect only prokaryotic cells.
 
 
4) A researcher lyses a cell that contains nucleic acid molecules and capsid units of TMV. He
leaves this sap in a covered test tube overnight. The next day he sprays this fluid on tobacco
plants. Which of the following would you expect to occur?

A) The plants would develop some but not all of the symptoms of the TMV infection.

B) The plants would become infected, but the sap from these plants would be unable to infect
other plants.

C) The plants would develop symptoms typically produced by viroids.

D) The plants would not show any disease symptoms.

E) The plants would develop the typical symptoms of TMV infection.

 
 

5) Which of the following statements best describes oncogenes?

A) They are found only in tumor cells.

B) They are found only in tumor-causing viruses.

C) Activation of a single oncogene can transform a healthy cell.

D) They code for growth factors or proteins associated with growth factors.

E) Both A and B accurately describe oncogenes.

 
 

6) Most molecular biologists believe that viruses originated from fragments of cellular nucleic
acid. Which of the following observations supports this theory?

A) Viruses can infect both prokaryotic and eukaryotic cells.

B) Viruses can reproduce only inside host cells.

C) Viruses are enclosed in protein capsids rather than plasma membranes.

D) Viruses contain either DNA or RNA.

E) Viral genomes are usually more similar to the genome of the host cell than to the genome of
other cells.
 
 
7) A virus injects its DNA into a cell. Some genes are transcribed quite rapidly. Those genes are
probably involved in

A) producing proteins that lyse the bacterial cell.

B) producing DNA polymerase.

C) producing viral capsule proteins.

D) producing repressor proteins to control the bacterial cell.

E) producing various enzymes to alter cellular metabolism.

 
 

8) For many bacteriophages, infections are self-limiting. Each phage that infects a cell produces
hundreds of new phages, and eventually cells are infected by several phages at different times.
This results in a competition for regulatory control over the cell, with the eventual result of the
death of the cell without the production of new viruses. This phenomenon is called
superinfection. Superinfection can be prevented by which of the following changes in the
bacteriophage?

A) making larger numbers of new phages

B) restricting the host range of the phage

C) slowing down the rate of the lytic infection

D) evolving a more complex protein coat

E) the virus becoming a prophage in the cell

 
 

9) Which of the following does NOT consist of a sequence of bases?

A) structural gene

B) regulator gene

C) repressor

D) operator
E) promoter
 
 

10) Virulent phages undergo a(n) ________ life cycle, whereas temperate phages are capable of
undergoing a(n) ________ cycle.

A) lytic; lysogenic

B) retroviral; infective

C) lysogenic; lytic

D) infective; retroviral

E) infective; benign
 
 

11) Viruses that have only a single strand of RNA are known as

A) proviruses.

B) lytic phages.

C) bacteriophages.

D) viroids.

E) retroviruses.
 
 

12) Of the following, which is LEAST related to the others?

A) viroids B) provirus C) viral envelope D) prophage

 
 

13) Of the following, which is LEAST related to the others?

A) nucleoid B) R plasmids C) episome D) prions E) F factor

 
 

14) Of the following, which is LEAST related to the others?

A) transformation

B) conjugation

C) induction

D) transposition

E) transduction
 
 

15) Of the following, which is LEAST related to the others?

A) repressor

B) promoter

C) operator

D) regulatory gene

E) prion
 
 

16) Of the following, which is LEAST related to the others?

A) inducer

B) cAMP receptor protein

C) repressor

D) corepressor

E) transposon
 
 

17) The host range of a virus is determined by

A) the viral coat.

B) enzymes produced by the virus before it infects the cell.

C) proteins on the surface of the cell.

D) whether the virus uses DNA or RNA.

E) both A and C.
 
 

18) Prions are infectious particles that are unique in that they are believed to lack

A) proteins.

B) DNA.

C) RNA.

D) any nucleic acid.

E) a membrane.
 
 

19) Which of the following is an example of transcriptional control of gene expression?

A) mRNA is stored in the cytoplasm and needs a control signal to initiate translation.

B) RNA processing occurs before mRNA exits the nucleus.

C) There is an amplification of genes for rRNA.

D) Transcription factors bind to the enhancer and promoter regions.

E) mRNA exists for a specific time before it is degraded.

 
 

20) All of the following are potential control mechanisms for regulation of gene expression in
eukaryotic organisms EXCEPT

A) the transport of mRNA from the nucleus.

B) the lactose operon.

C) gene amplification.

D) transcription.
E) the degradation of mRNA.
 
 

21) A eukaryotic gene typically has all of the following features EXCEPT

A) an operator.

B) a start base triplet.

C) a promoter.

D) introns.

E) a transcriptional stop message.

 
 

22) The gene that stimulates tumorogenesis in Burkitt's lymphoma is expressed when it is moved
to chromosome 14 from chromosome 8. This is an example of gene expression regulated by

A) gene amplification.

B) point mutations.

C) diffusible factors.

D) steroid hormones.

E) translocation.
 
 

23) Gene expression in eukaryotes may depend upon

A) the position of the gene on the chromosome.

B) the state of the external environment.

C) the stage of development of the organism.

D) A and C are correct.

E) A, B, and C are correct.

 
 
24) Steroid hormones produce their effects in cells by

A) promoting the degradation of specific mRNAs.

B) promoting the formation of looped domains in certain regions of DNA.

C) activating key enzymes in metabolic pathways.

D) activating translation of certain mRNAs.

E) promoting transcription of certain regions of DNA.

 
 

25) Eukaryotes use all of the following as a means of controlling gene expression EXCEPT the

A) modification of the amino acid sequence of a protein after it has been translated.

B) binding of regulatory proteins to DNA.

C) modification of the RNA nucleotides to enhance transcription.

D) degradation of mRNA molecules.

E) processing of the mRNA transcript before it can be transcribed.

 
 

26) Which of the following events is necessary for the production of a truly malignant tumor?

A) activation of an oncogene in the cell

B) the inactivation of tumor suppressor genes within the cell

C) the presence of a retrovirus within the cell

D) the presence of mutagenic substances within the cell's environment

E) Both A and B are necessary.

 
 

27) Which of the following statements concerning proto-oncogenes is FALSE?

A) They are similar to oncogenes found in retroviruses.

B) They are genes that code for proteins involved in cell division.

C) They are involved in producing proteins for cell adhesion.

D) They are produced by somatic mutations induced by carcinogenic substances.

E) They code for proteins associated with cell growth.

 
 

28) What percentage of the DNA in a typical eukaryotic cell is expressed at any given time?

A) 40-60% B) 3-5% C) 60-90% D) 5-20% E) 20-40%

 
 

29) In a nucleosome, what is the DNA wrapped around?

A) ribosomes

B) histones

C) polymerase molecules

D) nucleolus protein

E) mRNA
 
 

30) In eukaryotes, what is the active transcription generally associated with?

A) euchromatin only

B) both euchromatin and highly methylated DNA

C) very tightly packed DNA only

D) highly methylated DNA only

E) heterochromatin only
 
 

31) Muscle cells and nerve cells in one kind of animal owe their differences in structure to
A) having different chromosomes.

B) using different genetic codes.

C) expressing different genes.

D) having different genes.

E) having unique ribosomes.

 
 

32) Which of the following represents an order of increasingly higher levels of organization?

A) 30-nanometer chromatin fiber, nucleosome, looped domain

B) looped domain, nucleosome, 30-nanometer chromatin fiber

C) looped domain, 30-nanometer chromatin fiber, nucleosome

D) nucleosome, looped domain, 30-nanometer chromatin fiber

E) nucleosome, 30-nanometer chromatin fiber, looped domain

 
 

33) If one were to observe the activity of methylated DNA, it would be expected that it would

A) be unwinding in preparation for protein synthesis.

B) be replicating.

C) have turned off or slowed down the process of transcription.

D) induce protein synthesis by not allowing repressors to bind with it.

E) be very active in translation.

 
 

34) If the structure of a TV show is analogous to the structure of a gene, then the introns of a
gene would be analogous to

A) the opening theme music.

B) the segments of the show.

C) the commercials between shows.

D) the closing credits.

E) the commercials between segments of the show.

 
 

35) Which of the following is NOT a mechanism whereby a proto-oncogene is converted to an

oncogene?

A) point mutation

B) gene transposition

C) gene amplification

D) chromosome translocation

E) methylation of bases
 
 

36) Which of the following is LEAST related to the others?

A) 30-nm chromatin fiber

B) histones

C) looped domains

D) pseudogenes

E) nucleosomes
 
 

37) Approximately what proportion of the DNA in humans does NOT produce a protein or a
functional RNA?

A) 87% B) 17% C) 97% D) 54% E) 68%

 
 

38) Which of the following is NOT a characteristic of triplet-repeat disorders like Huntington's
disease?
A) In general, these disorders affect the nervous system.

B) The resulting protein has a string of adjacent glutamines.

C) The number of repeats tends to correlate with the severity of the disease.

D) The triplet is actually translated.

E) These disorders all tend to exhibit delayed onset; affected individuals do not show symptoms
for many years.
 
 

39) Biotechnology is presently being used to do which of the following?

A) produce vaccines

B) correct defects in human germ cells

C) produce human gene products

D) Only A and C are correct.

E) A, B, and C are correct.

 
 

40) It is theoretically possible for a gene from any organism to function in any other organism.
Why is this possible?

A) All organisms have the same genetic code.

B) All organisms are made up of cells.

C) All organisms have ribosomes.

D) All organisms have transfer RNA.

E) All organisms have similar nuclei.

 
 

41) If you discovered a bacterial cell that contained no restriction endonuclease, which of the
following would you expect to happen?

A) The cell would be unable to replicate its DNA.

B) The cell would be easily infected and lysed by bacteriophages.

C) The cell would create incomplete plasmids.

D) The cell would become an obligate parasite.

E) Both A and D would occur.

 
 

42) A DNA fingerprint is produced by

A) treating selected segments of DNA with restriction enzymes.

B) electrophoresis of restriction fragments.

C) oligonucleotides from PCRs.

D) electroporation of cDNAs.

E) Both A and B are correct.

 
 

43) Why is it difficult to get bacteria to express genes directly from eukaryotic DNA?

A) Eukaryotic genes may contain transposons.

B) Eukaryotic genes are not transcribed in a single transcript.

C) Eukaryotic genes contain introns.

D) Eukaryotic genes lack controlling regions.

E) Eukaryotic genes do not contain enhancer sequences.

 
 

The following questions refer to the techniques, tools, or substances below. Answers may be
used once, more than once, or not at all.

A. restriction enzymes

B. gene cloning

C. DNA ligase
D. gel electrophoresis

E. reverse transcriptase

44) produces many copies of a gene for basic research or for large-scale production of a gene
product

45) enables one to create complementary DNA (cDNA) from mRNA; results in a smaller gene
product (RNA processed; no introns) that is more easily translated by bacteria

46) separates molecules by movement due to size and electrical charge

47) seals the sticky ends of restriction fragments to make recombinant DNA
 
 

48) Restriction fragments of DNA are separated from one another by which process?

A) centrifugation

B) filtering

C) gel electrophoresis

D) chromatography

E) electron microscopy
 
 

49) What is a cloning vector?

A) the sticky end of a DNA fragment

B) a DNA probe used to locate a particular gene in the genome

C) an agent, such as a plasmid, used to transfer DNA from an in vitro solution into a living cell

D) the laboratory apparatus used to clone genes

E) the enzyme that cuts DNA into restriction fragments

 
 

50) Bacteria containing recombinant plasmids are often identified by which process?
A) producing antibodies specific for each bacterium containing a recombinant plasmid

B) examining the cells with an electron microscope

C) removing the DNA of all cells in a culture to see which cells have plasmids

D) exposing the bacteria to an antibiotic that kills the cells lacking the plasmid

E) using radioactive tracers to locate the plasmids

 
 

51) Plasmids are important in biotechnology because they are

A) surfaces for protein synthesis in eukaryotic recombinants.

B) recognition sites on recombinant DNA strands.

C) a vehicle for the insertion of recombinant DNA into bacteria.

D) proviruses incorporated into the host DNA.

E) surfaces for respiratory processes in bacteria.

 
 

52) What is the genetic function of restriction endonuclease?

A) cleaves nucleic acids at specific sites

B) adds new nucleotides to the growing strand of DNA

C) joins nucleotides during replication

D) joins nucleotides during transcription

E) repairs breaks in sugar-phosphate backbones

 
 

53) The Eco RI enzyme used in constructing hybrid molecules of certain gene sequences and
plasmid DNA acts by

A) allowing a hybrid plasmid DNA into a transformed molecule.

B) sealing plasmid DNA and foreign DNA into a closed circle.

C) opening DNA molecules at specific sites, leaving sticky ends exposed.

D) transcribing plasmid DNA into a transformed molecule.

E) binding human genes to bacterial plasmids.

 
 
 

I. transform E. coli cells

II. cleave by endonuclease

III. extract plasmid DNA from bacterial cells

IV. join plasmid DNA with foreign DNA by hydrogen bonds

V. seal with DNA ligase

54) From the list above, which of the following is the most logical sequence of steps for splicing
foreign DNA into a plasmid and inserting the plasmid into a bacterium?

A) IV, V, I, II, III

B) I, II, IV, III, V

C) III, IV, V, I, II

D) II, III, V, IV, I

E) III, II, IV, V, I

 
 

55) All of the following may function in signal transduction in plants EXCEPT

A) second messengers.

B) calcium ions.

C) receptor proteins.

D) nonrandom mutations.
E) phytochrome.
 
 

56) What is the function of calmodulin in a signal-transduction pathway?

A) to be a membrane-bound hormone receptor that causes an influx of Ca2+

B) to receive the stimulus and activate the second messenger in the transduction step

C) to form a complex with Ca2+ and activate specific molecules

D) to induce rapid responses such as stomatal closing or cell elongation

E) to induce the selective activation of genes

 
 

57) The effects of a plant hormone are dependent on which of the following?

A) concentrations of other hormones

B) concentration of the hormone

C) developmental stage of the plant

D) Only B and C are correct.

E) A, B, and C are correct.

 
 

For the following questions, match the hormone with the classic description of that hormone.
Each choice may be used once, more than once, or not at all.

A. auxin

B. cytokinin

C. gibberellin

D. ethylene

E. abscisic acid

58) a gas that hastens fruit ripening

59) promotes internode elongation; promotes germination of certain seeds
 
 

60) Plant hormones can be characterized by all of the following EXCEPT that they

A) affect division, elongation, and differentiation of cells.

B) control plant growth and development.

C) have a multiplicity of effects.

D) function independently of other hormones.

E) may act by altering gene expression.

 
 

61) Which of the following has NOT been established as an aspect of auxin's role in cell
elongation?

A) Auxin activity permits an increase in turgor pressure.

B) Auxin instigates a loosening of cell wall fibers.

C) Auxin increases the quantity of cytoplasm in the cell.

D) Through auxin activity, vacuoles increase in size.

E) Auxin stimulates proton pumps.

 
 

62) According to the acid growth hypothesis, auxin works by

A) greatly increasing the rate of deposition of cell wall material.

B) dissolving the cell membranes temporarily, permitting cells that were on the verge of dividing
to divide more rapidly.

C) dissolving sieve plates, permitting more rapid transport of nutrients.

D) allowing the affected cell walls to stretch.

E) changing the pH within the cell, which would permit the electron transport chain to operate
more efficiently.
 
 

63) The only known naturally occurring auxin is

A) IAA. B) TCA. C) GA. D) ABA. E) 2, 4-D.

 
 

64) Why is it so difficult to study the actions of plant hormones?

A) They often interact to produce an effect.

B) They sometimes cause different responses in different plants.

C) They are found in small quantities in the plant.

D) We probably have not discovered all of them.

E) All of the above make the study of plant hormones difficult.

 
 

65) An enzyme cascade

A) activates the parathyroid gland.

B) ends in steroid hormone release.

C) initiates regulation of the nervous system.

D) increases the response to a hormone.

E) takes several days to occur.

 
 

66) A varying response to a common chemical messenger is possible because

A) various target cells have different genes.

B) various target cells differ in their receptors to the same hormone.

C) each cell knows how it fits into the body's master plan.
D) the hormone is chemically altered in different ways as it travels through different branches of
the circulatory system.

E) the circulatory system regulates responses to hormones by routing the hormones to specific
targets.
 
 

67) Which hormone is NOT a steroid?

A) estrogen B) cortisone C) testosterone D) insulin E) androgen

 
 

68) Which of the following statements about hormones is CORRECT?

A) Steroid hormones affect the activity of certain proteins within the cell, whereas peptide
hormones directly affect the processing of mRNA.

B) Steroid and peptide hormones produce different effects but use the same biochemical
mechanisms.

C) Steroid hormones affect the synthesis of proteins, whereas peptide hormones affect the
activity of proteins already present in the cell.

D) Steroid hormones affect the synthesis of proteins to be exported from the cell, whereas
peptide hormones affect the synthesis of proteins that remain in the cell.

E) Steroid and peptide hormones produce the same effects but differ in the mechanisms that
produce the effects.
 
 

69) Frequently, very few molecules of a hormone are required to effect changes in a target cell.
This is because

A) the mechanism of hormonal action involves the rapid replication of the hormone within the
target cell to quickly magnify the hormone's effect.

B) the mechanism of hormonal action involves an enzyme cascade that amplifies the response to
a hormone.

C) hormones are large molecules that persist for years and can repeatedly stimulate the same cell.

D) hormones are lipid soluble and readily penetrate the membranes of the target cell.
E) the mechanism of hormonal action involves memory cells that have had prior contact with the
hormone and immediately respond to its presence.
 
 

70) Hormone X produces its effect in its target cells via the cAMP second messenger system. If
you expose a target cell to only a single molecule, which of the following will produce the
greatest effect?

A) a molecule of hormone X injected into the cytoplasm of the cell

B) a molecule of activated, cAMP-dependent protein kinase injected into the cytoplasm of the
cell

C) a molecule of cAMP injected into the cytoplasm of the cell

D) a molecule of hormone X applied to the extracellular fluid surrounding the cell

E) a molecule of cAMP applied to the extracellular fluid surrounding the cell