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.
Ch. 7 - Sex Determination and Sex Chromosomes
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 7, Problem 14
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?
Verified step by step guidance1
Understand the structure of the human sex chromosomes: the X and Y chromosomes pair and synapse during meiosis only in a small region called the pseudoautosomal region (PAR). This region allows for proper segregation of the sex chromosomes.
Recognize that genes located within the PAR are present on both the X and Y chromosomes and undergo recombination during meiosis, which helps maintain genetic similarity in this region.
Consider that male-determining genes, such as SRY, are typically located outside the PAR in the non-recombining region of the Y chromosome to prevent them from being exchanged with the X chromosome during meiosis.
Analyze the consequence if male-determining genes were located within the PAR: because this region recombines with the X chromosome, these genes could be transferred to the X chromosome during meiosis, potentially disrupting the strict male-specific inheritance pattern.
Conclude that such recombination could lead to abnormal sex determination outcomes, such as males inheriting an X chromosome with male-determining genes or females inheriting Y-linked male-determining genes, which could cause disorders of sexual development.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sex Chromosome Pairing and Synapsis
During meiosis, the X and Y chromosomes pair and synapse only in a small homologous region called the pseudoautosomal region. This limited synapsis allows for proper segregation of sex chromosomes. Genes located outside this region typically do not recombine between X and Y.
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10:35
Human Sex Chromosomes
Recombination and Gene Location on Sex Chromosomes
Recombination occurs in the pseudoautosomal region where X and Y chromosomes exchange genetic material. If male-determining genes were located within this region, they could be subject to recombination, potentially disrupting their male-specific function by mixing with X-linked alleles.
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10:35Human Sex Chromosomes
Male-Determining Genes and Sex Determination
Male-determining genes, such as SRY, are typically located on the non-recombining region of the Y chromosome to ensure stable inheritance of male sex traits. If these genes recombined with the X chromosome, it could lead to sex reversal or loss of male-specific characteristics.
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Related Practice
Textbook Question
Define the Lyon hypothesis.
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Textbook Question
Assume that on rare occasions the attached X chromosomes in female gametes become unattached. Based on the parental phenotypes in Problem 12, what outcomes in the F₁ generation would indicate that this has occurred during female meiosis?
Textbook Question
What is a Barr body, and where is it found in a cell?
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Textbook Question
When cows have twin calves of unlike sex (fraternal twins), the female twin is usually sterile and has masculinized reproductive organs. This calf is referred to as a freemartin. In cows, twins may share a common placenta and thus fetal circulation. Predict why a freemartin develops.
Textbook Question
An attached-X female fly, XXY, expresses the recessive X-linked white-eye mutation. It is crossed to a male fly that expresses the X-linked recessive miniature-wing mutation. Determine the outcome of this cross in terms of sex, eye color, and wing size of the offspring.