Effects of periodic selection on gene diversity in organelle genomes and other systems without recombination.
Effects of periodic selection on gene diversity in organelle genomes and other systems without recombination.
复制标题
周期性选择对细胞器基因组和其他系统中基因多样性的影响，无需重组。
DOI：
10.1093/genetics/127.2.449
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发表时间：
1991
期刊：
影响因子：
3.3
通讯作者：
BirkyJr,CW
中科院分区：
文献类型：
--
作者：
Maruyama,T;BirkyJr,CW
具有非常强连锁的基因组，如原核生物和真核细胞器中的基因组，受制于一种极端形式的搭便车，称为周期性选择。当一个有利的突变（以下简称“驱动突变”）发生在一个群体的基因组拷贝上，并进入固定状态时，整个染色体就固定了。因此，该染色体上的所有等位基因都通过搭便车固定下来，遗传多样性减少到零或几乎为零。多样性在突变的压力下再次增加，直到下一轮的周期性选择。在很长一段时间内，相对于有更多的重组，种群的平均多样性会因周期性选择而减少。搭便车也会出现在重组的生物体中，尽管多样性的减少会少一些。KAPLAN， HUDSON和LANGLEY（1989）展示了如何计算任何程度连锁搭便车的二倍体群体的预期多样性；读者可以参考他们的论文进行更详细的讨论和参考文献。本文给出了中性等位基因在不存在重组的情况下，在周期性选择影响下的期望多样性方程的一个更简单的推导。这个模型是一个完全无性的单倍体基因组。它也适用于有性生殖的生物体中的细胞器基因组，只要细胞器DNA的传递是严格的单亲性的，每个后代只从一个亲本那里接受细胞器基因；无论父母一方总是雌性，或者有时是雌性，有时是雄性，这都无关紧要。如果某些子代从父母双方获得细胞器DNA，只要父母双方的DNA分子之间没有重组，该模型仍然适用。只要每个细胞中的细胞器基因组拷贝通常相同且不重组，那么每个细胞包含许多细胞器基因组拷贝的事实就无关紧要了。我们假设在随机漂移、突变和周期性选择之间有一个有限种群处于平衡状态。种群通过突变的积累获得遗传多样性，并通过漂变达到平衡。这些突变都是中性或有效中性的，都是潜在的搭便车者。每隔一段时间，就会出现搭便车或周期性的选择事件，在这种选择事件中，有利的突变发生并被选择所固定。相对于中性突变率而言，固定所需的时间是如此之短，以至于群体被-
Genomes with very strong linkage, such as those in prokaryotes and eukaryotic organelles, are subject to an extreme form of hitchhiking called periodic selection. When an advantageous mutation (hereafter, the" driver") occurs in one copy of the genome in a population and it goes to fixation, the whole chromosome is fixed. Consequently all alleles on that chromosome are fixed by hitchhiking and genetic diversity is reduced to zero or nearly so. Diversity increases again under mutational pressure, until the next round of periodic selection. Over long time periods, the mean diversity of the population is reduced by periodic selection, relative to what it would be if there were more recombination. Hitchhiking will also be seen in organisms with recombination, although the reduction in diversity will be less. KAPLAN, HUDSON and LANGLEY (1989) showed how to calculate the expected diversity of a diploid population subject to hitchhiking with any degree of linkage; the reader is referred to their paper for more detailed discussion and references to the literature. Here we present a simpler derivation of the equation for the expected diversity of neutral alleles under the influence of periodic selection when there is no recombination. The model is for a completely asexual, haploid genome. It is also applicable to organelle genomes in a sexually reproducing organism so long as the transmission of organelle DNA is strictly uniparental, with each offspring receiving organelle genes from only one parent; it does not matter whether this parent is always the female, or sometimes the female and sometimes the male. If some progeny receive organelle DNA from both parents, the model is still applicable providing there is no recombination between DNA molecules from the two parents. The fact that each cell contains many copies of the organelle genome is irrelevant so long as the copies in each individual are usually identical and do not recombine. We assume a finite population at equilibrium between random drift, mutation, and periodic selection. The population acquires genetic diversity by the accumulation of mutations, balanced by drift. These mutations are all neutral or effectively neutral, and are all potential hitchhikers. At intervals there is a hitchhiking or periodic selection event in which an advantageous mutation occurs and is fixed by selection. The time required for fixation is so short relative to the neutral mutation rate that the population be-