Hughes Jennifer F, Skaletsky Helen, Pyntikova Tatyana, Minx Patrick J, Graves Tina, Rozen Steve, Wilson Richard K, Page David C
Howard Hughes Medical Institute, Whitehead Institute, and Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA.
Nature. 2005 Sep 1;437(7055):100-3. doi: 10.1038/nature04101.
The human Y chromosome, transmitted clonally through males, contains far fewer genes than the sexually recombining autosome from which it evolved. The enormity of this evolutionary decline has led to predictions that the Y chromosome will be completely bereft of functional genes within ten million years. Although recent evidence of gene conversion within massive Y-linked palindromes runs counter to this hypothesis, most unique Y-linked genes are not situated in palindromes and have no gene conversion partners. The 'impending demise' hypothesis thus rests on understanding the degree of conservation of these genes. Here we find, by systematically comparing the DNA sequences of unique, Y-linked genes in chimpanzee and human, which diverged about six million years ago, evidence that in the human lineage, all such genes were conserved through purifying selection. In the chimpanzee lineage, by contrast, several genes have sustained inactivating mutations. Gene decay in the chimpanzee lineage might be a consequence of positive selection focused elsewhere on the Y chromosome and driven by sperm competition.
人类Y染色体通过男性进行克隆传递，其含有的基因比它所演化而来的进行有性重组的常染色体要少得多。这种进化衰退的程度之深，导致有人预测Y染色体将在一千万年内完全丧失功能基因。尽管最近在大量Y连锁回文序列中发现基因转换的证据与这一假说相悖，但大多数独特的Y连锁基因并不位于回文序列中，也没有基因转换伙伴。因此，“即将消亡”假说取决于对这些基因的保守程度的理解。通过系统比较约六百万年前分化的黑猩猩和人类中独特的Y连锁基因的DNA序列，我们发现，在人类谱系中，所有这类基因都通过纯化选择得以保守。相比之下，在黑猩猩谱系中，有几个基因发生了失活突变。黑猩猩谱系中的基因衰退可能是Y染色体其他部位受到正选择并由精子竞争驱动的结果。
