Zhivotovsky L A, Feldman M W
Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia.
Proc Natl Acad Sci U S A. 1995 Dec 5;92(25):11549-52. doi: 10.1073/pnas.92.25.11549.
We analyze the within- and between-population dynamics of the distribution of the number of repeats at multiple microsatellite DNA loci subject to stepwise mutation. Analytical expressions for moments up to the fourth order within a locus and the variance of between-locus variance at mutation-drift equilibrium have been obtained. These statistics may be used to test the appropriateness of the one-step mutation model and to detect between-locus variation in the mutation rate. Published data are compatible with the one-step mutation model, although they do not reject the two-step model. Using both multinomial sampling and diffusion approximations for the analysis of the genetic distance introduced by Goldstein et al. [Goldstein, D. B., Linares, A. R., Cavalli-Sforza, L. L. & Feldman, M. W. (1995) Proc. Natl. Acad. Sci. USA 92, 6723-6727], we show that this distance follows a chi 2 distribution with degrees of freedom equal to the number of loci when there is no variation in mutation rates among the loci. In the presence of such variation, the variance of the distance is obtained. We conclude that the number of microsatellite loci required for the construction of phylogenetic trees with reliable branch lengths may be several hundred. Also, mutations that change repeat scores by several units, even though extremely rare, may dramatically influence estimates of population parameters.
我们分析了在逐步突变情况下，多个微卫星DNA位点重复数分布的群体内和群体间动态。已获得了在突变 - 漂变平衡时一个位点内直至四阶矩以及位点间方差的方差的解析表达式。这些统计量可用于检验一步突变模型的适用性，并检测突变率的位点间变异。已发表的数据与一步突变模型相符，尽管它们不排除两步模型。使用多项式抽样和扩散近似来分析由戈尔茨坦等人[戈尔茨坦，D. B.，利纳雷斯，A. R.，卡瓦利 - 斯福尔扎，L. L. & 费尔德曼，M. W.（1995年）《美国国家科学院院刊》92，6723 - 6727]引入的遗传距离，我们表明当各基因座间突变率无变化时，该距离服从自由度等于基因座数的卡方分布。在存在这种变异的情况下，获得了距离的方差。我们得出结论，构建具有可靠分支长度的系统发育树所需的微卫星基因座数量可能为数百个。此外，即使极为罕见，但能使重复分数改变几个单位的突变可能会显著影响群体参数的估计。
