Mammalian sex chromosomes evolved from an ordinary pair of autosomes. The X chromosome is highly conserved, whereas the Y chromosome varies among species in size, structure, and gene content. Unlike autosomes that contain randomly mixed collections of genes, the sex chromosomes are enriched in testis-biased genes related to sexual development and reproduction, particularly in spermatogenesis and male fertility. This review focuses on how sex chromosome dosage compensation takes place and why meiotic sex chromosome inactivation occurs during spermatogenesis. Furthermore, the review also emphasizes how testis-biased genes are enriched on the sex chromosomes and their functions in male fertility. It is concluded that sex chromosomes are critical to sexual development and male fertility; however, our understanding of how sex chromosome genes direct sexual development and fertility has been hampered by the structural complexities of the sex chromosomes and by the multicopy nature of the testis gene families that also play a role in immunity, cancer development, and brain function.

中文翻译：

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哺乳动物性别染色体的结构，基因含量以及在男性生育中的功能。

哺乳动物的性染色体是从一对普通的常染色体进化而来的。X染色体是高度保守的，而Y染色体在大小，结构和基因含量上随物种而异。与含有随机混合的基因集合的常染色体不同，性染色体富含与性发育和生殖有关的睾丸偏向基因，特别是在精子发生和男性生育方面。这篇综述着重于性染色体剂量补偿的发生方式以及在生精过程中为何发生减数分裂性染色体失活。此外，该综述还强调了睾丸偏向基因如何在性染色体上丰富及其在男性生育中的功能。结论是性染色体对性发育和男性生育至关重要。然而，