Nachman M W
Department of Ecology and Evolutionary Biology, Biosciences, University of Arizona, Tucson 85721, USA.
Genetica. 1998;102-103(1-6):61-9.
A simple neutral model predicts that the ratio of non-synonymous to synonymous fixed differences between species will be the same as the ratio of non-synonymous to synonymous polymorphisms within species. This prediction is tested with existing mitochondrial datasets from 25 animal species. In slightly over half of the studies, the ratio of replacement to silent polymorphisms within species is significantly greater than the ratio of replacement to silent fixed differences between species. These observations are best explained by a substantial number of mildly deleterious amino acid mutations that contribute to heterozygosity but rarely become fixed.
一个简单的中性模型预测，物种间非同义固定差异与同义固定差异的比率将与物种内非同义多态性与同义多态性的比率相同。利用来自25种动物的现有线粒体数据集对这一预测进行了检验。在略超过一半的研究中，物种内替换多态性与沉默多态性的比率显著高于物种间替换固定差异与沉默固定差异的比率。这些观察结果最好用大量轻度有害的氨基酸突变来解释，这些突变导致了杂合性，但很少固定下来。
