Textbook Question
Explain how the behavior of homologous chromosomes in meiosis parallels Mendel's law of segregation for autosomal alleles D and d. During which stage of M phase do these two alleles segregate from one another?
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Ch. 3 - Cell Division and Chromosome Heredity
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 3, Problem 10
How many Barr bodies are found in a normal human female nucleus? In a normal male nucleus?
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Understand what a Barr body is: it is an inactivated X chromosome found in the nuclei of cells in females, serving as a mechanism for dosage compensation between males and females.
Recall that normal human females have two X chromosomes (XX), while normal males have one X and one Y chromosome (XY).
Apply the formula for the number of Barr bodies: Number of Barr bodies = (Number of X chromosomes) - 1.
For a normal female (XX), calculate the number of Barr bodies as , so Barr bodies = .
For a normal male (XY), calculate the number of Barr bodies as , so Barr bodies = .
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Barr Body
A Barr body is an inactivated X chromosome found in the nuclei of female cells. It appears as a dense, dark-staining spot and represents the mechanism of dosage compensation to balance gene expression between males and females.
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02:51
Other Chromatin Modifications
X Chromosome Inactivation
X chromosome inactivation is the process by which one of the two X chromosomes in females is randomly silenced during early embryonic development. This ensures that females, like males, have one functional copy of the X chromosome in each cell.
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09:30X-Inactivation
Sex Chromosome Composition in Humans
Normal human females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). This difference determines the number of Barr bodies: females typically have one Barr body, and males have none.
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Related Practice
Textbook Question
Suppose crossover occurs between the homologous chromosomes in the previous problem. At what stage of M phase do alleles D and d segregate?
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Textbook Question
Alleles A and a are on one pair of autosomes, and alleles B and b are on a separate pair of autosomes. Does crossover between one pair of homologs affect the expected proportions of gamete genotypes? Why or why not? Does crossover between both pairs of chromosomes affect the expected gamete proportions? Why or why not?
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Textbook Question
Describe the role of the following structures or proteins in cell division:
Microtubules
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Textbook Question
Describe the role of the following structures or proteins in cell division:
Cohesin protein
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Textbook Question
Describe the role of the following structures or proteins in cell division:
Kinetochores
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