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Ch. 3 - Cell Division and Chromosome Heredity
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 3, Problem 2b

Our closest primate relative, the chimpanzee, has a diploid number of 2n = 48. For each of the following stages of M phase, identify the number of chromosomes present in each cell.
Meiotic metaphase I

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1
Understand that the diploid number (2n) represents the total number of chromosomes in a somatic cell of the organism. For chimpanzees, 2n = 48, meaning there are 48 chromosomes in a diploid cell.
Recall that meiosis is a type of cell division that reduces the chromosome number by half, producing haploid (n) gametes. However, in metaphase I of meiosis, the cell is still diploid because homologous chromosomes are paired but not yet separated.
In meiotic metaphase I, homologous chromosomes align at the metaphase plate. Each homologous pair consists of two chromosomes, and since the cell is still diploid at this stage, the total number of chromosomes remains 48.
Note that while the number of chromosomes remains 48, each chromosome consists of two sister chromatids because DNA replication occurred during the S phase of interphase prior to meiosis.
Conclude that the number of chromosomes in a cell during meiotic metaphase I for a chimpanzee is 48, with each chromosome consisting of two sister chromatids.

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Key Concepts

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

Diploid Number

The diploid number (2n) refers to the total number of chromosomes in a somatic cell, which includes two sets of chromosomes, one from each parent. In the case of chimpanzees, the diploid number is 48, meaning they have 24 pairs of homologous chromosomes. Understanding diploidy is crucial for determining chromosome numbers during various stages of cell division.
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Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid cells from one diploid cell. It consists of two sequential divisions: meiosis I and meiosis II. During meiosis I, homologous chromosomes are separated, which is essential for producing gametes with half the genetic material of the parent organism.
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Metaphase I

Metaphase I is a stage in meiosis where homologous chromosome pairs align at the cell's equatorial plane. At this point, each pair consists of two sister chromatids, and the cell is still diploid. For chimpanzees, during meiotic metaphase I, there would be 24 pairs of chromosomes, totaling 48 chromosomes, as they have not yet been separated into haploid cells.
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