Kennedy P, Nachman M W
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
Genetics. 1998 Sep;150(1):359-68. doi: 10.1093/genetics/150.1.359.
Statistical analyses of DNA sequences have revealed patterns of nonneutral evolution in mitochondrial DNA of mice, humans, and Drosophila. Here we report patterns of mitochondrial sequence evolution in South American marsh rats (genus Holochilus). We sequenced the complete mitochondrial ND3 gene in 82 Holochilus brasiliensis and 21 H. vulpinus to test the neutral prediction that the ratio of nonsynonymous to synonymous nucleotide changes is the same within and between species. Within H. brasiliensis we observed a greater number of amino acid polymorphisms than expected based on interspecific comparisons. This contingency table analysis suggests that many amino acid polymorphisms are mildly deleterious. Several tests of the frequency distribution also revealed departures from a neutral, equilibrium model, and these departures were observed for both nonsynonymous and synonymous sites. In general, an excess of rare sites was observed, consistent with either a recent selective sweep or with populations not at mutation-drift equilibrium.
对DNA序列的统计分析揭示了小鼠、人类和果蝇线粒体DNA中的非中性进化模式。在此，我们报告南美沼泽鼠（Holochilus属）线粒体序列的进化模式。我们对82只巴西沼泽鼠（Holochilus brasiliensis）和21只狐色沼泽鼠（H. vulpinus）的线粒体ND3基因进行了测序，以检验非同义核苷酸变化与同义核苷酸变化的比率在物种内和物种间相同这一中性预测。在巴西沼泽鼠中，我们观察到的氨基酸多态性数量比基于种间比较预期的要多。这种列联表分析表明，许多氨基酸多态性具有轻度有害性。对频率分布的几次检验也揭示了与中性平衡模型的偏离，并且在非同义位点和同义位点均观察到了这种偏离。总体而言，观察到稀有位点过多，这与近期的选择性清除或未处于突变 - 漂变平衡的种群一致。
