Nachman M W
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson 85721, USA.
Mol Biol Evol. 1998 Dec;15(12):1744-50. doi: 10.1093/oxfordjournals.molbev.a025900.
DNA sequences from the nonrecombining portion of the Y chromosome were compared with autosomal and X-linked sequences from mice and humans to test the neutral prediction that ratios of polymorphism to divergence are the same for different genes. Intraspecific variation within Mus domesticus was compared with divergence between M. domesticus and Mus caroli for Sry, a region 5' to Sry, and four X-linked genes, Hprt, Plp, Amg, and Glra2. None of these comparisons revealed significantly reduced variation on the Y chromosome. Intraspecific variation within humans was compared with divergence between humans and chimpanzees for three Y-linked loci (Zfy, the YAP region, and the Sry region), seven X-linked loci (Il2rg, Plp, Hprt, Gk, Ids, Pdhal, and Dmd), and the beta-globin locus on chromosome 11. In these comparisons, the observed level of variation on the human Y chromosome was slightly lower than expected, but was significantly lower in only one case (Sry region vs. Dmd). These results suggest that the levels of variability on the Y chromosome in mice and humans are close to expected values given the effective population size and mutation rates for these loci. There is at most only a modest reduction in variability that may be attributed to natural selection (either genetic hitchhiking or background selection).
将Y染色体非重组部分的DNA序列与小鼠和人类的常染色体及X连锁序列进行比较，以检验多态性与分化率对于不同基因而言是相同的这一中性预测。将家鼠的种内变异与家鼠和小家鼠之间的分化进行比较，涉及Sry、Sry 5'端的一个区域以及四个X连锁基因Hprt、Plp、Amg和Glra2。这些比较均未显示Y染色体上的变异显著减少。将人类的种内变异与人类和黑猩猩之间的分化进行比较，涉及三个Y连锁基因座（Zfy、YAP区域和Sry区域）、七个X连锁基因座（Il2rg、Plp、Hprt、Gk、Ids、Pdhal和Dmd）以及11号染色体上的β-珠蛋白基因座。在这些比较中，人类Y染色体上观察到的变异水平略低于预期，但仅在一种情况下（Sry区域与Dmd相比）显著较低。这些结果表明，鉴于这些基因座的有效种群大小和突变率，小鼠和人类Y染色体上的变异水平接近预期值。至多只有适度的变异减少，这可能归因于自然选择（基因搭便车或背景选择）。
