Campbell Biology

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

Chapter 13

Meiosis and Sexual Life Cycles - all with Video Answers

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Chapter Questions

Problem 1

A human cell containing 22 autosomes and a Y chromosome is
a. a sperm.
b. an egg.
c. a zygote.
d. a somatic cell of a male.

Nicole Hewett

Nicole Hewett

Numerade Educator

Problem 2

Homologous chromosomes move toward opposite poles of a dividing cell during
a. mitosis.
b. meiosis I.
c. meiosis II.
d. fertilization.

Nicole Hewett

Numerade Educator

Problem 3

Meiosis II is similar to mitosis in that
a. sister chromatids separate during anaphase.
b. DNA replicates before the division.
c. the daughter cells are diploid.
d. homologous chromosomes synapse.

Nicole Hewett

Numerade Educator

Problem 4

If the DNA content of a diploid cell in the $G_{1}$ phase of the cell cycle is $x,$ then the DNA content of the same cell at metaphase of meiosis I would be
a. $0.25 x .$ b. $0.5 x$
c. $x .$ d. $2 x$

Nicole Hewett

Numerade Educator

Problem 5

If we continued to follow the cell lineage from question $4,$ then the DNA content of a single cell at metaphase of meiosis II would be
a. $0.25 x$. b. $0.5 x$. c. $x$. d. $2 x$

Nicole Hewett

Numerade Educator

Problem 6

The diagram at right shows a cell in meiosis.
(a) Label the appropriate structures with these terms, drawing lines or brackets as needed: chromosome (label as duplicated or unduplicated), centromere, kinetochore, sister chromatids, nonsister chromatids, homologous pair, homologs, chiasma, sister chromatid cohesion, alleles (of the $F$ and $H$ genes).
(b) Describe the makeup of a haploid set and a diploid set.
(c) Identify the stage of meiosis shown.

Nicole Hewett

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Problem 7

How can you tell that the cell in question 6 is undergoing meiosis, not mitosis?

Nicole Hewett

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Problem 8

Many species can reproduce either asexually or sexually. What might be the evolutionary significance of the switch from asexual to sexual reproduction that occurs in some organisms when the environment becomes unfavorable?

Nicole Hewett

Numerade Educator

Problem 9

The diagram in question 6 represents just a few of the chromosomes of a meiotic cell in a certain person. A previous study has shown that the freckles gene is located at the locus marked F, and the hair-color gene is located at the locus marked $\mathrm{H}$, both on the long chromosome. The individual from whom this cell was taken has inherited different alleles for each gene ("freckles" and "black hair" from one parent, and "no freckles" and "blond hair" from the other). Predict allele combinations in the gametes resulting from this meiotic event. (It will help if you draw out the rest of meiosis, labeling alleles by name.) List other possible combinations of these alleles in this individual's gametes.

Nicole Hewett

Numerade Educator

Problem 10

The continuity of life is based on heritable information in the form of DNA. In a short essay (100-150 words), explain how chromosome behavior during sexual reproduction in animals ensures perpetuation of parental traits in offspring and, at the same time, genetic variation among offspring.

Nicole Hewett

Numerade Educator

Problem 11

The Cavendish banana is the most popular fruit in the world, but is currently threatened by extinction due to a fungal agent (see the photo). This banana variety is "triploid" (3 $n$, with three sets of chromosomes) and can only reproduce through cloning by cultivators. Given what you know about meiosis, explain how the banana's triploid number accounts for its seedless condition. Considering genetic diversity, discuss how the absence of sexual reproduction might contribute to the vulnerability of this domesticated species to infectious agents.

Nicole Hewett

Numerade Educator