Department of Zoology, 6270 University Boulevard, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Trends Genet. 2011 Sep;27(9):358-67. doi: 10.1016/j.tig.2011.05.001.
Sex chromosomes differ from other chromosomes in the striking divergence they often show in size, structure, and gene content. Not only do they possess genes controlling sex determination that are restricted to either the X or Y (or Z or W) chromosomes, but in many taxa they also include recombining regions. In these 'pseudoautosomal regions' (PARs), sequence homology is maintained by meiotic pairing and exchange in the heterogametic sex. PARs are unique genomic regions, exhibiting some features of autosomes, but they are also influenced by their partial sex linkage. Here we review the distribution and structure of PARs among animals and plants, the theoretical predictions concerning their evolutionary dynamics, the reasons for their persistence, and the diversity and content of genes that reside within them. It is now clear that the evolution of the PAR differs in important ways from that of genes in either the non-recombining regions of sex chromosomes or the autosomes.
性染色体在大小、结构和基因组成上常常表现出明显的差异，与其他染色体不同。它们不仅拥有只存在于 X 或 Y（或 Z 或 W）染色体上的控制性别决定的基因，而且在许多分类群中还包括重组区域。在这些“假常染色体区域”（PARs）中，通过在异型性别的减数分裂配对和交换来维持序列同源性。PARs 是独特的基因组区域，表现出一些常染色体的特征，但它们也受到部分性连锁的影响。本文综述了 PAR 在动物和植物中的分布和结构、关于其进化动态的理论预测、它们持续存在的原因以及位于其中的基因的多样性和内容。现在已经清楚的是，PAR 的进化在重要方面与性染色体非重组区域或常染色体上的基因的进化不同。
