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Ch. 2 - Mitosis and Meiosis
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Not the one you use?Change textbook
Chapter 2, Problem 13

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

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1
Begin by defining spermatogenesis and oogenesis as the processes of male and female gamete formation, respectively, highlighting that both occur through meiosis but have distinct outcomes.
Explain spermatogenesis as a continuous process producing four viable sperm cells from each primary spermatocyte, emphasizing equal cytokinesis and the goal of producing motile gametes.
Describe oogenesis as an intermittent process resulting in one large ovum and smaller polar bodies due to unequal cytokinesis, which conserves cytoplasm in the ovum.
Discuss the formation of polar bodies as a mechanism to discard extra haploid sets of chromosomes while preserving most of the cytoplasm in the single ovum, which is crucial for early embryonic development.
Summarize the significance of polar bodies in ensuring that the ovum has sufficient nutrients and organelles to support the embryo, contrasting this with the production of multiple sperm cells optimized for mobility.

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Key Concepts

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

Spermatogenesis

Spermatogenesis is the process by which male gametes, or sperm cells, are produced in the testes. It involves a series of mitotic and meiotic divisions resulting in four haploid sperm cells from each primary spermatocyte, ensuring genetic diversity and continuous sperm production.
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Oogenesis

Oogenesis is the formation of female gametes, or ova, in the ovaries. Unlike spermatogenesis, it produces one viable egg and smaller polar bodies through unequal cytokinesis during meiosis, conserving cytoplasm in the egg to support early embryonic development.
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Formation and Significance of Polar Bodies

Polar bodies are small cells produced during oogenesis that contain excess genetic material but minimal cytoplasm. Their formation allows the egg to retain most of the cytoplasm, which is crucial for nourishing the embryo after fertilization, while discarding extra chromosomes to maintain haploidy.
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Related Practice
Textbook Question

Define and discuss these terms:

(a) synapsis

(b) bivalents

(c) chiasmata

(d) crossing over

(e) chromomeres

(f) sister chromatids

(g) tetrads

(h) dyad

(i) monads

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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?

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Textbook Question

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?

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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

(c) haploid cells following both divisions of meiosis

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Textbook Question

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.

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Textbook Question

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?

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