Selective Sweeps in Multilocus Models of Quantitative Traits
Selective Sweeps in Multilocus Models of Quantitative Traits
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DOI：
10.1534/genetics.112.142547
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发表时间：
2012-09-01
期刊：
影响因子：
3.3
通讯作者：
Stephan, Wolfgang
中科院分区：
文献类型：
--
作者：
Pavlidis, Pavlos;Metzler, Dirk;Stephan, Wolfgang
我们研究的轨迹的等位基因，影响多基因性状选择朝向表型最佳。此外，在此轨迹的条件下，我们分析了所选择的突变对连锁中性变异的影响。我们研究了良好的特点，两个位点的两个等位基因模型，但我们也提供了结果的双等位基因模型与多达8个位点。首先，当最佳表型是双杂合子在一个两个位点的模型，并没有显性或上位性的影响性状，所选择的突变的轨迹很少达到固定，相反，在两个位点的多态性平衡接近。是否达到多态性平衡（而不是在两个基因座上固定）取决于选择的强度和每个基因座上的纯合子到最佳状态的相对距离。此外，如果两个基因座对性状有相似的影响，那么当一个等位基因以低频率开始而另一个基因座是多态的（等位基因在中间频率）时，在给定基因座上的等位基因固定不太可能。较弱的选择增加了所研究的等位基因固定的概率，因为在这种情况下多态性平衡不太稳定。当我们不要求双杂合子处于最佳状态时，我们发现多态性平衡更难达到，固定变得更可能。第二，增加基因座的数量会降低固定的可能性，因为通过等位基因的各种组合，适应最佳状态是可能的。在选定的基因座旁边的系谱（身高、总长度和不平衡）和序列多态性（多态性数量、频谱和单倍型结构）的总结取决于选定的突变在平衡时接近的频率。我们的结论是，多位点的选择反应可能在某些情况下，防止选择性扫描完成，如在以前的研究中所描述的，但导致这种情况发生的条件强烈依赖于性状的遗传结构，固定选定的突变可能在许多情况下。
We study the trajectory of an allele that affects a polygenic trait selected toward a phenotypic optimum. Furthermore, conditioning on this trajectory we analyze the effect of the selected mutation on linked neutral variation. We examine the well-characterized two-locus two-allele model but we also provide results for diallelic models with up to eight loci. First, when the optimum phenotype is that of the double heterozygote in a two-locus model, and there is no dominance or epistasis of effects on the trait, the trajectories of selected mutations rarely reach fixation; instead, a polymorphic equilibrium at both loci is approached. Whether a polymorphic equilibrium is reached (rather than fixation at both loci) depends on the intensity of selection and the relative distances to the optimum of the homozygotes at each locus. Furthermore, if both loci have similar effects on the trait, fixation of an allele at a given locus is less likely when it starts at low frequency and the other locus is polymorphic (with alleles at intermediate frequencies). Weaker selection increases the probability of fixation of the studied allele, as the polymorphic equilibrium is less stable in this case. When we do not require the double heterozygote to be at the optimum we find that the polymorphic equilibrium is more difficult to reach, and fixation becomes more likely. Second, increasing the number of loci decreases the probability of fixation, because adaptation to the optimum is possible by various combinations of alleles. Summaries of the genealogy (height, total length, and imbalance) and of sequence polymorphism (number of polymorphisms, frequency spectrum, and haplotype structure) next to a selected locus depend on the frequency that the selected mutation approaches at equilibrium. We conclude that multilocus response to selection may in some cases prevent selective sweeps from being completed, as described in previous studies, but that conditions causing this to happen strongly depend on the genetic architecture of the trait, and that fixation of selected mutations is likely in many instances.