Textbook Question
Cat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females. Why are they certain of this?
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Ch. 5 - Sex Determination and Sex Chromosomes
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 5, Problem 18
Define the Lyon hypothesis.
Verified step by step guidance1
Understand that the Lyon hypothesis is a concept in genetics related to X chromosome inactivation in female mammals.
Recognize that females have two X chromosomes, but to balance gene expression with males (who have one X chromosome), one X chromosome in each cell is inactivated.
Know that the Lyon hypothesis states this inactivation occurs randomly in each cell early in embryonic development, leading to a mosaic pattern of gene expression.
Note that the inactivated X chromosome condenses into a structure called a Barr body, which is transcriptionally inactive.
Summarize that the Lyon hypothesis explains dosage compensation, ensuring that females do not produce twice the amount of X-linked gene products compared to males.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
X-Chromosome Inactivation
X-chromosome inactivation is a process in female mammals where one of the two X chromosomes is randomly silenced to balance gene expression with males, who have only one X chromosome. This ensures dosage compensation between sexes.
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09:30
X-Inactivation
Lyon Hypothesis
The Lyon hypothesis proposes that in female mammals, one X chromosome in each cell is randomly inactivated early in embryonic development, leading to mosaic expression of X-linked genes. This explains phenomena like calico cat coat patterns.
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03:13Translation:Wobble Hypothesis
Dosage Compensation
Dosage compensation is the mechanism that balances the expression of X-linked genes between males (XY) and females (XX). X-chromosome inactivation is a key form of dosage compensation in mammals.
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00:52Purpose of X Inactivation
Related Practice
Textbook Question
It has been suggested that any male-determining genes contained on the Y chromosome in humans cannot be located in the limited region that synapses with the X chromosome during meiosis. What might be the outcome if such genes were located in this region?
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Textbook Question
What is a Barr body, and where is it found in a cell?
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Textbook Question
Indicate the expected number of Barr bodies in interphase cells of individuals with Klinefelter syndrome, Turner syndrome, and karyotypes 47, XYY, 47, XXX, and 48, XXXX.
Textbook Question
Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?
Textbook Question
Predict the potential effect of the Lyon hypothesis on the retina of a human female heterozygous for the X-linked red-green color blindness trait.
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