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Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 10 - Eukaryotic Chromosome Abnormalities and Molecular OrganizationProblem 29b
Chapter 10, Problem 29b

A eukaryote with a diploid number of 2n=6 carries the chromosomes shown below and labeled (a) to (f).
Illustration of six chromosomes labeled (a) to (f), showing their alignment during metaphase in a diploid eukaryote.


Explain how you determined the correct alignment of homologous chromosomes on opposite sides of the metaphase plate. 

Verified step by step guidance
1
Understand the diploid number (2n=6), which indicates there are 6 chromosomes in total, organized into 3 homologous pairs. Each homologous pair consists of one chromosome inherited from each parent.
Identify homologous chromosomes by matching them based on size, centromere position, and banding patterns. For example, chromosomes labeled (a) and (b) might form one homologous pair, (c) and (d) another, and (e) and (f) the third pair.
Recall that during metaphase of mitosis, homologous chromosomes align along the metaphase plate. Each chromosome in a homologous pair is positioned on opposite sides of the plate, ensuring proper segregation during anaphase.
Consider the role of spindle fibers and kinetochores. Spindle fibers attach to the kinetochores of each chromosome, pulling them toward opposite poles. This ensures that homologous chromosomes are correctly aligned and segregated.
Verify the alignment by ensuring that each homologous pair is positioned symmetrically on opposite sides of the metaphase plate, with no mismatches or errors in pairing. This step is crucial for maintaining genetic integrity during cell division.

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Key Concepts

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

Homologous Chromosomes

Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence but may carry different alleles. Each parent contributes one chromosome to the pair, and during meiosis, these chromosomes align at the metaphase plate. Understanding their alignment is crucial for ensuring proper segregation during cell division.
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Chromosome Structure

Metaphase Plate

The metaphase plate is an imaginary plane that is equidistant from the two spindle poles during metaphase of cell division. It is where chromosomes align before being separated into daughter cells. Proper alignment on the metaphase plate is essential for accurate chromosome distribution, preventing aneuploidy.
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Meiosis Steps

Chromosome Pairing and Alignment

During metaphase, homologous chromosomes pair up and align along the metaphase plate, with one chromosome of each pair facing each spindle pole. This alignment is facilitated by the spindle apparatus, which ensures that each daughter cell receives one chromosome from each homologous pair. Correct pairing is vital for genetic stability and diversity.
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Related Practice
Textbook Question

A small population of deer living on an isolated island is separated for many generations from a mainland deer population. The populations retain the same number of chromosomes but hybrids are infertile. One chromosome (shown here) has a different banding pattern in the island population than in the mainland population.

In a mainland–island hybrid deer, recombination takes place in band q1 of the homologous chromosomes. Draw the gametes that result from this event.

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Textbook Question

A small population of deer living on an isolated island is separated for many generations from a mainland deer population. The populations retain the same number of chromosomes but hybrids are infertile. One chromosome (shown here) has a different banding pattern in the island population than in the mainland population.

Suppose that 40% of all meioses in mainland–island hybrids involve recombination somewhere in the chromosome region between q2.1 and p2. What proportion of the gametes of hybrid deer are viable? What is the cause of the decreased proportion of viable gametes in hybrids relative to the parental populations?

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Textbook Question

A eukaryote with a diploid number of 2n=6 carries the chromosomes shown below and labeled (a) to (f).

Carefully examine and redraw these chromosomes in any valid metaphase I alignment. Draw and label the metaphase plate, and label each chromosome with its assigned letter. 

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Textbook Question

Human chromosome 5 and the corresponding chromosomes from chimpanzee, gorilla, and orangutan are shown here. Describe any structural differences you see in the other primate chromosomes in relation to the human chromosome.

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Textbook Question

For the following crosses, determine as accurately as possible the genotypes of each parent, the parent in whom nondisjunction occurs, and whether nondisjunction takes place in the first or second meiotic division. Both color blindness and hemophilia, a blood-clotting disorder, are X-linked recessive traits. In each case, assume the parents have normal karyotypes.

A man and a woman who each has the wild-type phenotype have a son with Klinefelter syndrome (XXY) who has hemophilia.

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Textbook Question

For the following crosses, determine as accurately as possible the genotypes of each parent, the parent in whom nondisjunction occurs, and whether nondisjunction takes place in the first or second meiotic division. Both color blindness and hemophilia, a blood-clotting disorder, are X-linked recessive traits. In each case, assume the parents have normal karyotypes.

A man who is color blind and a woman who is wild type have a son with Jacob syndrome (XYY) who has hemophilia.

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