In species with separate sexes, sex determination often has a genetic basis, and in a wide diversity of taxa a pair of cytologically distinguishable 'sex chromosomes' are found such that the chromosome complements of males and females differ (males are often XY and females XX, but sometimes females are ZW whereas males are ZZ). Recent evidence from sequences of sex-linked genes confirms classical genetic evidence that these chromosomes are a homologous pair, evolved from a normal chromosome pair, between which recombination stopped. We discuss why sex chromosomes evolve reduced recombination and why different parts of the chromosomes stopped recombining at different times, and outline some of the consequences of suppressed recombination, including the evolution of chromosome heteromorphism.

中文翻译：

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性染色体限制性重组的进化。

在具有不同性别的物种中，性别决定通常具有遗传基础，并且在广泛多样的分类群中发现了一对细胞学上可区分的“性染色体”，使得雄性和雌性的染色体互补不同（雄性通常为 XY，雌性为 XX ，但有时女性是 ZW 而男性是 ZZ）。最近来自性相关基因序列的证据证实了经典遗传证据，即这些染色体是同源对，从正常染色体对进化而来，两者之间的重组停止。我们讨论了为什么性染色体进化减少重组以及为什么染色体的不同部分在不同时间停止重组，并概述了抑制重组的一些后果，包括染色体异型性的进化。