Department of Zoology, University of Cambridge, UK.
Bioessays. 2010 Jan;32(1):82-90. doi: 10.1002/bies.200900108.
If natural selection chose where new mutations occur it might well favour placing them near existing polymorphisms, thereby avoiding disruption of areas that work while adding novelty to regions where variation is tolerated or even beneficial. Such a system could operate if heterozygous sites are recognised and 'repaired' during the initial stages of crossing over. Such repairs involve an extra round of DNA replication, providing an opportunity for further mutations, thereby raising the local mutation rate. If so, the changes in heterozygosity that occur when populations grow or shrink could feed back to modulate both the rate and the distribution of mutations. Here, I review evidence from isozymes, microsatellites and single nucleotide polymorphisms that this potential is realised in real populations. I then consider the likely implications, focusing particularly on how these processes might affect microsatellites, concluding that heterozygosity does impact on the rate and distribution of mutations.
如果自然选择决定了新突变发生的位置，那么它很可能会倾向于将它们放置在现有多态性附近，从而避免破坏工作区域，同时为可容忍甚至有益的变异区域增添新的内容。如果杂合位点在交叉过程的初始阶段被识别并“修复”，那么这种系统就可以运行。这种修复涉及一轮额外的 DNA 复制，为进一步突变提供了机会，从而提高了局部突变率。如果是这样，当种群增长或收缩时，杂合性的变化可能会反馈回来，调节突变的速率和分布。在这里，我回顾了同工酶、微卫星和单核苷酸多态性的证据，表明这种潜力在实际种群中得以实现。然后，我考虑了可能的影响，特别关注这些过程如何影响微卫星，得出的结论是杂合性确实会影响突变的速率和分布。
