Charlesworth B
Department of Ecology and Evolution, University of Chicago, IL 60637-1573.
Genet Res. 1994 Jun;63(3):213-27. doi: 10.1017/s0016672300032365.
This paper analyses the effects of selection against deleterious alleles maintained by mutation ('background selection') on rates of evolution and levels of genetic diversity at weakly selected, completely linked, loci. General formulae are derived for the expected rates of gene substitution and genetic diversity, relative to the neutral case, as a function of selection and dominance coefficients at the loci in question, and of the frequency of gametes that are free of deleterious mutations with respect to the loci responsible for background selection. As in the neutral case, most effects of background selection can be predicted by considering the effective size of the population to be multiplied by the frequency of mutation-free gametes. Levels of genetic diversity can be sharply reduced by background selection, with the result that values for sites under selection approach those for neutral variants subject to the same regime of background selection. Rates of fixation of slightly deleterious mutations are increased by background selection, and rates of fixation of advantageous mutations are reduced. The properties of sex-linked and autosomal loci in random-mating populations are compared, and the effects of background selection on asexual and self-fertilizing populations are considered. The implications of these results for the interpretation of studies of molecular evolution and variation are discussed.
本文分析了针对由突变维持的有害等位基因的选择（“背景选择”）对弱选择、完全连锁位点上的进化速率和遗传多样性水平的影响。相对于中性情况，推导了基因替换预期速率和遗传多样性的通用公式，这些公式是所讨论位点上选择系数和显性系数以及相对于负责背景选择的位点不含有害突变的配子频率的函数。与中性情况一样，背景选择的大多数影响可以通过考虑种群的有效大小乘以无突变配子的频率来预测。背景选择可大幅降低遗传多样性水平，结果是选择位点的值接近处于相同背景选择模式下中性变体的值。背景选择会增加轻微有害突变的固定速率，降低有利突变的固定速率。比较了随机交配种群中X连锁和常染色体位点的特性，并考虑了背景选择对无性和自交种群的影响。讨论了这些结果对分子进化和变异研究解释的意义。
