Population genetics of polymorphism and divergence.
Population genetics of polymorphism and divergence.
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作者：
S. Sawyer;D. Hartl
突变位点的频率被建模为泊松随机场在两个物种，共享一个足够近的共同祖先。新等位基因的选择效应可以是有利的、中性的或有害的。该模型被应用到果蝇模拟和果蝇yakuba的乙醇脱氢酶基因（Adh）的核苷酸的样本配置。假设同义突变率为1.5 × 10 ~（-8）/位点/年，10代/年，我们得到了有效种群大小（N（e）= 6.5 × 10 ~（-6））、物种分化时间（E）和物种分化时间（E）的估计值。（tdiv = 374万年），平均选择系数（对于有利的或轻度有害的置换，σ = 1.53 × 10（-6）/代），尽管可以想到仅选择两个氨基酸置换，其余为中性。分析，其中包括一个独立的无限位点模型与选择的抽样理论，还建议的估计，在酶中的氨基酸的数量是容易受到有利的突变是在2-23的范围内，在任何一个时间。该方法为使用2 × 2列联表比较固定差异和多态位点与沉默位点和氨基酸替换提供了理论基础。
Frequencies of mutant sites are modeled as a Poisson random field in two species that share a sufficiently recent common ancestor. The selective effect of the new alleles can be favorable, neutral, or detrimental. The model is applied to the sample configurations of nucleotides in the alcohol dehydrogenase gene (Adh) in Drosophila simulans and Drosophila yakuba. Assuming a synonymous mutation rate of 1.5 x 10(-8) per site per year and 10 generations per year, we obtain estimates for the effective population size (N(e) = 6.5 x 10(6)), the species divergence time (tdiv = 3.74 million years), and an average selection coefficient (sigma = 1.53 x 10(-6) per generation for advantageous or mildly detrimental replacements), although it is conceivable that only two of the amino acid replacements were selected and the rest neutral. The analysis, which includes a sampling theory for the independent infinite sites model with selection, also suggests the estimate that the number of amino acids in the enzyme that are susceptible to favorable mutation is in the range 2-23 at any one time. The approach provides a theoretical basis for the use of a 2 x 2 contingency table to compare fixed differences and polymorphic sites with silent sites and amino acid replacements.