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6: Sex Chromosomes Sex Linkage

Last updated

Sep 22, 2024
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- 5.S: Genetic Analysis of Multiple Genes (Summary)
- 6.1: Introduction

Ying Liu
City College of San Francisco

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6.1: Introduction
This page details key learning objectives on autosomes versus sex chromosomes, sex-linkage exceptions to Mendel’s First Law, and inheritance patterns of sex-linked traits in Drosophila melanogaster. It explains the role of the Y chromosome in sex determination, highlights Y-linked traits, and contrasts autosomal with sex-linked inheritance using human and turkey genetics examples, supported by visuals and a video resource.
6.2: Autosomes and Sex Chromosomes
This page explains that diploid organisms have chromosome pairs, including autosomes and sex chromosomes, with humans having XY males and XX females. It highlights the role of sex chromosomes in sex determination and their unique behavior during meiosis based on whether an individual is homogametic or heterogametic. Additionally, it addresses misconceptions about the names of these chromosomes, clarifying that their names do not correspond to their physical shapes.
6.3: Pseudo-Autosomal Regions on the X and Y Chromosomes
This page discusses the evolutionary divergence of the X and Y chromosomes, leading to significant gene loss on the Y chromosome. Despite their differences, they can pair during meiosis through pseudo-autosomal regions, enabling crossover. These regions include genes like SHOX, which affects height and may cause health issues in conditions such as Turner syndrome. Both XY males and XX females have two copies of these genes, while chromosomal aneuploidies can cause anomalies in gene expression.
6.4: Sex Linkage- An Exception to Mendel's First Law
This page explains the inheritance of sex chromosomes and autosomes, focusing on X-linked genes like the white gene in Drosophila melanogaster. It details how X-linked alleles are inherited with examples of mutations affecting eye color. The text emphasizes reciprocal crosses to identify sex-linkage, showcasing differences in offspring phenotypes. It also references Thomas Morgan's work, which established that genes reside on chromosomes.
6.5: Y-Linked Genes
This page discusses the Y chromosome, containing about 200 genes mainly related to male sex determination and fertility, with the SRY gene playing a key role. It highlights unique Y-linked traits and the concept of paternal inheritance, noting that Y-linked traits impact only male offspring and that the dominance-recessive paradigm is not applicable due to the presence of a single allele in males.
6.6: Chapter 10 Summary
This page explains the distinction between autosomes and sex chromosomes, detailing the pairing of autosomes and the unique aspects of sex chromosomes. It covers pseudo-autosomal regions that facilitate recombination between X and Y chromosomes, and illustrates how sex-linked genes diverge from Mendelian inheritance due to sex chromosome influence and dosage compensation. Examples from Drosophila and birds are provided.
6.7: Key Terms in Chapter 10
6.8: Chapter 10 Study Questions
6.9: Chapter 10 Answers

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