Lehmann T, Hawley W A, Collins F H
Division of Parasitic Diseases, Centers for Disease Control and Prevention, Chamblee, Georgia 30341, USA.
Genetics. 1996 Nov;144(3):1155-63. doi: 10.1093/genetics/144.3.1155.
A test to evaluate constraints on the evolution of single microsatellite loci is described. The test assumes that microsatellite alleles that share the same flanking sequence constitute a series of alleles with a common descent that is distinct from alleles with a mutation in the flanking sequence. Thus two or more different series of alleles at a given locus represent the outcomes of different evolutionary processes. The higher rate of mutations within the repeat region (10(-3) or 10(-4)) compared with that of insertion/deletion or point mutations in adjacent flanking regions (10(-9)) or with that of recombination between the repeat and the point mutation (10(-6) for sequences 100 bp long) provides the rationale for this assumption. Using a two-phase, stepwise mutation model we simulated the evolution of a number of independent series of alleles and constructed the distributions of two similarity indices between pairs of these allele series. Applying this approach to empirical data from locus AG2H46 of Anopheles gambiae resulted in a significant excess of similarity between the main and the null series, indicating that constraints affect allele distribution in this locus. Practical considerations of the test are discussed.
描述了一种评估单个微卫星基因座进化限制的测试方法。该测试假设共享相同侧翼序列的微卫星等位基因构成一系列具有共同祖先的等位基因，这与侧翼序列发生突变的等位基因不同。因此，给定基因座上两个或更多不同系列的等位基因代表不同进化过程的结果。与相邻侧翼区域的插入/缺失或点突变（10^(-9)）或与重复序列和点突变之间的重组（对于100 bp长的序列为10^(-6)）相比，重复区域内较高的突变率（10^(-3)或10^(-4)）为这一假设提供了依据。使用两阶段逐步突变模型，我们模拟了多个独立等位基因系列的进化，并构建了这些等位基因系列对之间两个相似性指数的分布。将这种方法应用于冈比亚按蚊AG2H46基因座的经验数据，结果表明主要系列和无效系列之间存在显著的相似性过剩，表明限制影响了该基因座的等位基因分布。讨论了该测试的实际考虑因素。
