前进两步，后退一步：有利等位基因的多效性效应
Two steps forward, one step back: the pleiotropic effects of favoured alleles.
作者信息
Otto Sarah P
机构信息
Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
出版信息
Proc Biol Sci. 2004 Apr 7;271(1540):705-14. doi: 10.1098/rspb.2003.2635.
Pleiotropy is one of the most commonly observed attributes of genes. Yet the extent and influence of pleiotropy have been underexplored in population genetics models. In this paper, I quantify the extent to which pleiotropy inhibits the spread of alleles in response to directional selection on a focal trait. Under the assumption that pleiotropic effects are extensive and deleterious, the fraction of alleles that are beneficial overall is severely limited by pleiotropy and rises nearly linearly with the strength of directional selection on the focal trait. Over a broad class of distribution of pleiotropic effects, the mean selective effect of those alleles that are beneficial overall is halved, on average, by pleiotropy. The fraction of new mutant alleles that are beneficial overall and that succeed in fixing within a population is even more severely limited when directional selection is weak, but it rises quadratically with the strength of directional selection. Finally, the mean selective effect of mutant alleles that are beneficial and succeed in fixing is reduced by one-third, on average, by pleiotropy. These results help to shape our understanding of the evolutionary inertia caused by pleiotropy.
基因多效性是基因最常见的特性之一。然而，在群体遗传学模型中，基因多效性的程度及其影响尚未得到充分研究。在本文中，我量化了在针对某一重点性状的定向选择作用下，基因多效性抑制等位基因传播的程度。假设基因多效性效应广泛且有害，那么总体上有益的等位基因比例会受到基因多效性的严重限制，并随对重点性状的定向选择强度近似线性增加。在广泛的基因多效性效应分布类别中，总体上有益的那些等位基因的平均选择效应，因基因多效性平均减半。当定向选择较弱时，总体上有益且成功在群体中固定下来的新突变等位基因比例受到的限制更为严重，但它随定向选择强度呈二次方增加。最后，有益且成功固定的突变等位基因的平均选择效应，因基因多效性平均降低三分之一。这些结果有助于塑造我们对由基因多效性导致的进化惰性的理解。
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