Essentials of Genetics

William S. Klug, Michael R. Cummings, Charlotte A. Spencer

Chapter 2

Mitosis and Meiosis - all with Video Answers

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Chapter Questions

Problem 1

In this chapter, we focused on how chromosomes are distributed during cell division, both in dividing somatic cells (mitosis) and in gamete- and spore-forming cells (meiosis). We found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, answer the following questions.
(a) How do we know that chromosomes exist in homologous pairs?
(b) How do we know that DNA replication occurs during interphase, not early in mitosis?
(c) How do we know that mitotic chromosomes are derived from chromatin?

Khalida Dawar

Khalida Dawar

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Problem 2

Review the Chapter Concepts list on page $12 .$ All of these pertain to conceptual issues involving mitosis or meiosis. Based on these concepts, write a short essay that contrasts mitosis and meiosis, including their respective roles in organisms, the mechanisms by which they achieve their respective outcomes, and the consequences should either process fail to be executed with absolute fidelity.

Jackson Miner

Numerade Educator

Problem 3

What role do the following cellular components play in the storage, expression, or transmission of genetic information:
chromatin, (b) nucleolus, (c) ribosome, (d) mitochondrion, centriole, (f) centromere?

Jackson Miner

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Problem 4

Discuss the concepts of homologous chromosomes, diploidy, and haploidy. What characteristics do two homologous chromosomes share?

Patina Herring

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Problem 5

If two chromosomes of a species are the same length and have similar centromere placements and yet are not homologous, what is different about them?

Bryan Valdivia

Numerade Educator

Problem 6

Describe the events that characterize each stage of mitosis.

Jackson Miner

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Problem 7

How are chromosomes named on the basis of their centromere
placement?

Jackson Miner

Numerade Educator

Problem 8

Contrast telophase in plant and animal mitosis.

Prashant Bana

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Problem 9

Describe the phases of the cell cycle and the events that characterize each phase.

Jackson Miner

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Problem 10

Define and discuss these terms: (a) synapsis, (b) bivalents, (c) chiasmata, (d) crossing over, (e) sister chromatids, (f) tetrads,
$(g)$ dyads, (h) monads.

Bryan Valdivia

Numerade Educator

Problem 11

Contrast the genetic content and the origin of sister versus nonsister chromatids during their earliest appearance in prophase I of meiosis. How might the genetic content of these change by the time tetrads have aligned at the equatorial plate during metaphase I?

Marisa A

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Problem 12

Given the end results of the two types of division, why is it necessary for homologs to pair during meiosis and not desirable for them to pair during mitosis?

Patina Herring

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Problem 13

Contrast spermatogenesis and oogenesis. What is the significance of the formation of polar bodies?

Jackson Miner

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Problem 14

Explain why meiosis leads to significant genetic variation while mitosis does not.

Jackson Miner

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Problem 15

A diploid cell contains three pairs of homologous chromosomes designated Cl and $\mathrm{C} 2, \mathrm{M} 1$ and $\mathrm{M} 2$, and $\mathrm{S} 1$ and $\mathrm{S} 2$. No crossing over occurs. What combinations of chromosomes are possible in (a) daughter cells following mitosis,
(b) cells undergoing the first meiotic metaphase, (c) haploid cells following both divisions of meiosis?

Patina Herring

Numerade Educator

Problem 16

Considering Problem $15,$ predict the number of different haploid cells that could be produced by meiosis if a fourth chromosome pair (W1 and W2) were added.

Patina Herring

Numerade Educator

Problem 17

During oogenesis in an animal species with a haploid number of
$6,$ one dyad undergoes nondisjunction during meiosis II. Following the second meiotic division, this dyad ends up intact in the ovum. How many chromosomes are present in (a) the mature ovum and
(b) the second polar body?
(c) Following fertilization by a normal sperm, what chromosome condition is created?

Bryan Valdivia

Numerade Educator

Problem 18

What is the probability that, in an organism with a haploid number of $10,$ a sperm will be formed that contains all 10 chromosomes whose centromeres were derived from maternal homologs?

Bryan Valdivia

Numerade Educator

Problem 19

The nuclear DNA content of a single sperm cell in Drosophila melanogaster is approximately 0.18 picogram. What would be the expected nuclear DNA content of a primary spermatocyte in Drosophila? What would be the expected nuclear DNA content of a somatic cell (non-sex cell) in the Gl phase? What would be the expected nuclear DNA content of a somatic cell at metaphase?

Bryan Valdivia

Numerade Educator

Problem 20

Describe the role of meiosis in the life cycle of a vascular plant.

Jennifer Stoner

Jennifer Stoner

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Problem 21

Contrast the chromatin fiber with the mitotic chromosome. How are the two structures related?

Jackson Miner

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Problem 22

Describe the "folded-fiber" model of the mitotic chromosome.

Jennifer Stoner

Jennifer Stoner

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Problem 23

You are given a metaphase chromosome preparation (a slide) from an unknown organism that contains 12 chromosomes. Two that are clearly smaller than the rest appear identical in length and centromere placement. Describe all that you can about these chromosomes.

Jennifer Stoner

Jennifer Stoner

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Problem 24

If one follows 50 primary oocytes in an animal through their various stages of oogenesis, how many secondary oocytes would be formed? How many first polar bodies would be formed? How many ootids would be formed? If one follows 50 primary spermatocytes in an animal through their various stages of spermatogenesis, how many secondary spermatocytes would be formed? How many spermatids would be formed?

Jackson Miner

Numerade Educator

Problem 25

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
In mitosis, what chromatid combination(s) will be present during metaphase? What combination(s) will be present at each pole at the completion of anaphase?

Patina Herring

Numerade Educator

Problem 26

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
During meiosis I, assuming no crossing over, what chromatid combination(s) will be present at the completion of prophase I? Draw all possible alignments of chromatids as migration begins during early anaphase.

Patina Herring

Numerade Educator

Problem 27

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
Are there any possible combinations present during prophase of meiosis II other than those that you drew in Problem $26 ?$ If $s 0$ draw them.

Patina Herring

Numerade Educator

Problem 28

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
Draw all possible combinations of chromatids during the early phases of anaphase in meiosis II.

Patina Herring

Numerade Educator

Problem 29

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
Assume that during meiosis I none of the $C$ chromosomes disjoin at metaphase, but they separate into dyads (instead of monads) during meiosis II. How would this change the alignments that you constructed during the anaphase stages in meiosis I and II? Draw them.

Patina Herring

Numerade Educator

Problem 30

Consider a diploid cell that contains three pairs of chromosomes designated $\mathrm{AA}, \mathrm{BB},$ and $\mathrm{CC}$. Each pair contains a maternal and a paternal member (e.g., $A^{m}$ and $A^{p}$ ). Using these designations, demonstrate your understanding of mitosis and meiosis by drawing chromatid combinations as requested. Be sure to indicate when chromatids are paired as a result of replication and/or synapsis. You may wish to use a large piece of brown manila wrapping paper or a cut-up paper grocery bag for this project and to work in partnership with another student. We recommend cooperative learning as an efficacious way to develop the skills you will need for solving the problems presented throughout this text.
Assume that each gamete resulting from Problem 29 fuses, in fertilization, with a normal haploid gamete. What combinations will result? What percentage of zygotes will be diploid, containing one paternal and one maternal member of each chromosome pair?

Patina Herring

Numerade Educator