Wiehe T
Department of Integrative Biology, University of California, Berkeley, USA.
Theor Popul Biol. 1998 Jun;53(3):272-83. doi: 10.1006/tpbi.1997.1346.
Microsatellite variation and the mechanisms which are responsible for this variation have received much attention in the last few years. Most theoretical studies of microsatellite allele distributions, however, did not incorporate the evolutionary dynamics of linked sites. The dynamics is usually modeled by invoking a special mutation mechanism such as stepwise mutation, which leads to a stepwise increase or decrease of the number of motif repeats on the occasion of mutation. It is shown here that selection at a locus, which itself is not subject to mutation, but which is adjacent to a microsatellite locus has an influence on statistics of the microsatellite allele distribution, provided that mutation rates are low to intermediate, when compared to 1/t1, the inverse of the time to fixation of a linked favorable substitution. If mutation rates are high, as for example in humans, a selective effect upon the microsatellite locus, such as hitchhiking, will quickly be obscured by mutations. In particular, in the latter case, the model shows that no correlation is to be expected between recombination rates and variability of microsatellites--such as had been predicted and experimentally demonstrated for nucleotide variability and recombination rates in Drosophila. The present model is a generalization of the two locus two allele hitchhiking model which had been studied by Stephan and co-workers.
微卫星变异及其产生机制在过去几年中受到了广泛关注。然而，大多数关于微卫星等位基因分布的理论研究并未纳入连锁位点的进化动态。这种动态通常通过引入特殊的突变机制（如逐步突变）来建模，逐步突变会导致在突变时基序重复数目的逐步增加或减少。本文表明，在一个本身不发生突变但与微卫星位点相邻的位点上进行选择，会对微卫星等位基因分布的统计产生影响，前提是与连锁有利替代固定时间的倒数1/t1相比，突变率处于低到中等水平。如果突变率很高，比如在人类中，对微卫星位点的选择效应（如搭便车效应）将很快被突变掩盖。特别是在后一种情况下，该模型表明，在重组率和微卫星变异性之间预计不会存在相关性——就像之前针对果蝇核苷酸变异性和重组率所预测和实验证明的那样。本模型是对Stephan及其同事研究的双位点双等位基因搭便车模型的推广。
