Twomey M J, Feldman M W
Department of Biological Sciences, Stanford University, California 94305.
Theor Popul Biol. 1990 Apr;37(2):320-42. doi: 10.1016/0040-5809(90)90042-t.
Two diallelic loci in an infinite panmictic population of diploid individuals are modelled. The A/a locus is subject to unidirectional mutation and either multiplicative fertility selection or, equivalently, sex-asymmetric viability selection. The M/m locus acts as a selectively neutral modifier of the mutation rate at A/a. The loci recombine at rate R. If the M/m locus is initially monomorphic, and the A/a locus has reached equilibrium, the fate of a new modifier allele is found to depend not just on its relative effect on mutation but also upon the linkage, R. Each initial equilibrium may be characterized by a critical value of the recombination rate, R*. If 0 less than R* less than 0.5, a sufficiently small "down" modifier of the mutation rate will invade the population when R less than R* whereas a sufficiently small "up" modifier will succeed when R greater than R*. If R* less than 0 or R* greater than 0.5, only mutation reduction may occur. Numerical analysis of 56,000 sample equilibria indicates that mutation rates may be increased, but only when the selection regime is such that the A/a locus would remain polymorphic in the absence of mutation.
对二倍体个体组成的无限随机交配群体中的两个双等位基因位点进行建模。A/a位点存在单向突变，并受到乘法生育率选择，或者等效地，受到性别不对称生存力选择。M/m位点作为A/a位点突变率的选择性中性修饰基因。两个位点以速率R进行重组。如果M/m位点最初是单态的，且A/a位点已达到平衡，那么发现一个新的修饰基因等位基因的命运不仅取决于其对突变的相对影响，还取决于连锁关系R。每个初始平衡都可以由重组率的临界值R来表征。如果0 < R < 0.5，当R < R时，一个足够小的突变率“向下”修饰基因将侵入群体，而当R > R时，一个足够小的“向上”修饰基因将成功侵入。如果R* < 0或R* > 0.5，则只会发生突变率降低的情况。对56000个样本平衡的数值分析表明，突变率可能会增加，但前提是选择模式使得在没有突变的情况下A/a位点仍保持多态性。
