Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, United Kingdom.
Mol Biol Evol. 2010 Mar;27(3):661-70. doi: 10.1093/molbev/msp282. Epub 2009 Nov 18.
Genes linked to sex chromosomes may show different levels of functional change than autosomal genes due to different evolutionary pressures. We used whole-genome data from zebra finch-chicken orthologs to test for Faster-Z evolution, finding that Z-linked genes evolve up to 50% more rapidly than autosomal genes. We combined these divergence data with information about sex-specific expression patterns in order to determine whether the Faster-Z Effect that we observe was predominantly the result of positive selection of recessive beneficial mutations in the heterogametic sex or primarily due to genetic drift attributable to the lower effective population size of the Z chromosome compared with an autosome. The Faster-Z Effect was no more prevalent for genes expressed predominantly in females; therefore, our data indicate that the largest source of Faster-Z Evolution is the increased levels of genetic drift on the Z chromosome. This is likely a product of sexual selection acting on males, which reduces the effective population size of the Z relative to that of the autosomes. Additionally, this latter result suggests that the relative evolutionary pressures underlying Faster-Z Evolution are different from those in analogous Faster-X Evolution.
由于受到不同进化压力的影响，与性染色体相关的基因可能会表现出与常染色体基因不同的功能变化。我们使用斑马雀-鸡直系同源基因的全基因组数据来检验快速-Z 进化，发现 Z 连锁基因的进化速度比常染色体基因快多达 50%。我们将这些分歧数据与性别的特定表达模式信息相结合，以确定我们观察到的快速-Z 效应主要是由于异配子性别中隐性有益突变的正选择，还是主要归因于与常染色体相比，Z 染色体的有效种群规模较低导致的遗传漂变。在主要在雌性中表达的基因中，快速-Z 效应并不更为普遍；因此，我们的数据表明，快速-Z 进化的最大来源是 Z 染色体上遗传漂变水平的增加。这可能是雄性中性选择作用的产物，它降低了 Z 相对于常染色体的有效种群规模。此外，后一个结果表明，快速-Z 进化背后的相对进化压力与类似的快速-X 进化不同。
