12| INHERITANCE
REVIEW QUESTIONS
1. Which event leads to a diploid cell in a life cycle?
a. meiosis
b. fertilization
c. alternation of generations
d. mutation
2. Meiosis produces daughter cells.
a. two haploid
b. two diploid
c. four haploid
d. four diploid
3. At which stage of meiosis are sister chromatids separated from each other?
a. prophase I
b. prophase II
c. anaphase I
d. anaphase II
4. The part of meiosis that is similar to mitosis is .
a. meiosis I
b. anaphase I
c. meiosis II
d. interkinesis
5. If a muscle cell of a typical organism has 32 chromosomes, how many chromosomes will be in a gamete of that
same organism?
a. 8
b. 16
c. 32
d. 64
6. The genotype XXY corresponds to:
a. Klinefelter syndrome
b. Turner syndrome
c. Triplo-X
d. Jacob syndrome
7. Abnormalities in the number of X chromosomes tend to be milder than the same abnormalities in autosomes because
of .
a. deletions
b. nonhomologous recombination
c. synapsis
d. X inactivation
8. Aneuploidies are deleterious for the individual because of what phenomenon?
a. nondisjunction
b. gene dosage
c. meiotic errors
d. X inactivation
9. In addition to codominance, the ABO blood group antigens are also an example of .
a. incomplete dominance
b. X-linked recessive inheritance
c. multiple alleles
d. recessive lethal inheritance
10. Zoe parents are normal but she has cystic fibrosis. Which of the following is the most likely explanation?
a. Zoe probably inherited one faulty allele from her father, who is a carrier, and one normal allele from her
mother.
b. Zoe probably inherited one faulty allele from her mother, who must also have cystic fibrosis, and one normal
allele from her father.
c. Zoe must have inherited faulty alleles from both parents, both of whom must also have cystic fibrosis.
d. Zoe must have inherited faulty alleles from both parents, both of whom are carriers.
Point to Ponder:
11. In what ways is meiosis II similar to and different from mitosis of a diploid cell?
12. Individuals with trisomy 21 are more likely to survive to adulthood than individuals with trisomy 18. Based on
what you know about aneuploidies from this module, what can you hypothesize about chromosomes 21 and 18?
CRITICAL THINKING QUESTIONS
13. Explain the advantage that populations of sexually reproducing organisms have over asexually reproducing
organisms?
The offspring of sexually reproducing organisms are all genetically unique. Because of this, sexually reproducing organisms
may have more successful survival of offspring in environments that change than asexually reproducing organisms, whose
offspring are all genetically identical. In addition, the rate of adaptation of sexually reproducing organisms is higher, because
of their increased variation. This may allow sexually reproducing organisms to adapt more quickly to competitors and
parasites, who are evolving new ways to exploit or outcompete them.
14. Explain how the random alignment of homologous chromosomes during metaphase I contributes to variation in
gametes produced by meiosis.
Random alignment leads to new combinations of traits. The chromosomes that were originally inherited by the gamete-
producing individual came equally from the egg and the sperm. In metaphase I, the duplicated copies of these maternal and
paternal homologous chromosomes line up across the center of the cell to form a tetrad. The orientation of each tetrad is
random. There is an equal chance that the maternally derived chromosomes will be facing either pole. The same is true of
the paternally derived chromosomes. The alignment should occur differently in almost every meiosis. As the homologous
chromosomes are pulled apart in anaphase I, any combination of maternal and paternal chromosomes will move toward each
pole. The gametes formed from these two groups of chromosomes will have a mixture of traits from the individual’s parents.
Each gamete is unique.
15. Explain why it was essential that Mendel perform his crosses using a large sample size?
By using large sample sizes, Mendel minimized the effect of random variability resulting from chance. This allowed him to
identify true ratios corresponding to dominant–recessive inheritance.
16. How can a female carrier of an X-linked recessive disorder have a daughter who is affected?
The daughter received a faulty allele from mother and another faulty allele from father.
