Selection in finite populations with multiple alleles. 3. Genetic divergence with centripetal selection and mutation.
Selection in finite populations with multiple alleles. 3. Genetic divergence with centripetal selection and mutation.
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作者：
B. Latter
中等水平的基因或酶活性的自然选择已被证明会导致易受突变和随机遗传漂移影响的群体中出现高频率的杂种优势多态性。该模型假设突变变异谱是对称的，大多数变异对生存概率只有很小的影响。每个突变事件都会产生一个对人群来说是新奇的变体。等位基因效应被认为是酶活性规模上的累加性，只要杂合子的平均活性水平比群体中其他基因型更接近最佳水平，就会产生杂种优势。提出了一种群体之间遗传差异的新测量方法，该方法很容易从遗传学上解释，并且在向心选择、漂移和突变下随时间近似线性增加。该参数与顺反子在进化时间跨度内突变变化的积累率密切相关。对人类和果蝇多态性基因座的已发表数据的调查表明，基于杂合分子优越性的替代模型并不具有普遍重要性。电泳上产生杂交区的 13 个基因座的平均杂合子频率为 0.22 +/-.06，而分类为不产生杂合酶的 16 个基因座的平均杂合子频率为 0.23 +/-.04。
Natural selection for an intermediate level of gene or enzyme activity has been shown to lead to a high frequency of heterotic polymorphisms in populations subject to mutation and random genetic drift. The model assumes a symmetrical spectrum of mutational variation, with the majority of variants having only minor effects on the probability of survival. Each mutational event produces a variant which is novel to the population. Allelic effects are assumed to be additive on the scale of enzyme activity, heterosis arising whenever a heterozygote has a mean level of activity closer to optimal than that of other genotypes in the population.-A new measure of genetic divergence between populations is proposed, which is readily interpreted genetically, and increases approximately linearly with time under centripetal selection, drift and mutation. The parameter is closely related to the rate of accumulation of mutational changes in a cistron over an evolutionary time span.-A survey of published data concerning polymorphic loci in man and Drosophila suggests than an alternative model, based on the superiority of hybrid molecules, is not of general importance. Thirteen loci giving rise to hybrid zones on electrophoresis have a mean heterozygote frequency of 0.22 +/-.06, compared with a value of 0.23 +/-.04 for 16 loci classified as producing no hybrid enzyme.