The hitch-hiking effect of a favourable gene
The hitch-hiking effect of a favourable gene
复制标题
DOI：
10.1017/s0016672308009579
复制
发表时间：
2007-10-01
影响因子：
1.5
通讯作者：
Haigh, John
中科院分区：
文献类型：
--
作者：
Smith, John Maynard;Haigh, John
当一个选择性有利的基因替换发生在一个群体中，基因频率的变化将发生在紧密连锁的基因座。在中性多态性的情况下，平均杂合性将降低到随着与被取代基因座的距离而变化的程度。替代对中性多态性的总体影响是估计的;在总大小为10（6）或更多（也许是10（4）或更多）的群体中，这种影响将比随机固定更重要。这可以解释为什么自然群体中多态性的程度并没有像人们从考虑不同大小群体中突变和随机固定之间的平衡所期望的那样变化。对于在连锁基因座上选择性维持的多态性，只有当它导致完全固定时，这个过程才是重要的。如果在连锁基因座的选择系数是小的相比，在取代的基因座，它表明，在连锁基因座的完全固定的概率约为exp（- Nc），其中c是重组分数和N的人口规模。因此，在一个大的群体中，顺反子中可能发生选择性取代，而不消除同一顺反子中选择性维持的多态性。
When a selectively favourable gene substitution occurs in a population, changes in gene frequencies will occur at closely linked loci. In the case of a neutral polymorphism, average heterozygosity will be reduced to an extent which varies with distance from the substituted locus. The aggregate effect of substitution on neutral polymorphism is estimated; in populations of total size 10(6) or more (and perhaps of 10(4) or more), this effect will be more important than that of random fixation. This may explain why the extent of polymorphism in natural populations does not vary as much as one would expect from a consideration of the equilibrium between mutation and random fixation in populations of different sizes. For a selectively maintained polymorphism at a linked locus, this process will only be important in the long run if it leads to complete fixation. If the selective coefficients at the linked locus are small compared to those at the substituted locus, it is shown that the probability of complete fixation at the linked locus is approximately exp (- Nc), where c is the recombinant fraction and N the population size. It follows that in a large population a selective substitution can occur in a cistron without eliminating a selectively maintained polymorphism in the same cistron.