Ch. 2 - Mitosis and Meiosis

Klug - Concepts of Genetics 12th Edition

Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook

Klug 12th Edition

Ch. 2 - Mitosis and Meiosis

Problem 12

Chapter 2, 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?

Verified step by step guidance

Step 1: Understand the fundamental difference between mitosis and meiosis in terms of chromosome number and genetic content. Mitosis produces two genetically identical diploid daughter cells, while meiosis produces four genetically diverse haploid gametes.

Step 2: Recognize that during meiosis, homologous chromosomes pair up (synapsis) to allow for crossing over and recombination, which increases genetic diversity and ensures proper segregation of homologs into different gametes.

Step 3: Note that pairing of homologs during meiosis is necessary to align chromosomes so that the first meiotic division (meiosis I) separates homologous chromosomes, reducing the chromosome number by half.

Step 4: Contrast this with mitosis, where homologous chromosomes do not pair because the goal is to maintain the chromosome number and produce identical daughter cells; pairing could lead to improper segregation and genetic abnormalities.

Step 5: Conclude that homolog pairing is essential in meiosis for genetic variation and reduction division, but undesirable in mitosis because it would disrupt the faithful replication and distribution of identical chromosomes.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Homologous Chromosome Pairing in Meiosis

During meiosis, homologous chromosomes pair up to allow for crossing over and proper segregation. This pairing ensures genetic recombination and reduces chromosome number by half, producing haploid gametes essential for sexual reproduction.

Differences Between Mitosis and Meiosis

Mitosis results in two genetically identical diploid daughter cells for growth and repair, while meiosis produces four genetically diverse haploid cells for reproduction. The processes differ in chromosome behavior, especially in homolog pairing and segregation.

Consequences of Homolog Pairing in Mitosis

If homologous chromosomes paired during mitosis, it could lead to improper chromosome segregation and genetic instability. Mitosis requires sister chromatids to separate to maintain chromosome number and genetic consistency in daughter cells.

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Related Practice

Textbook Question

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?

Textbook Question

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

Textbook Question

A diploid cell contains three pairs of homologous chromosomes designated C1 and C2, M1 and M2, and S1 and S2. No crossing over occurs. What combinations of chromosomes are possible in?

(a) daughter cells following mitosis

(b) cells undergoing the first meiotic metaphase

Textbook Question

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

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Textbook Question

Define and discuss these terms:

(a) synapsis

(b) bivalents

(d) crossing over

(e) chromomeres

(f) sister chromatids