Otto S P, Gerstein A C
Department of Zoology, University of British Columbia, 6270 University Blvd, Vancouver, BC, Canada V6T1Z4.
Biochem Soc Trans. 2006 Aug;34(Pt 4):519-22. doi: 10.1042/BST0340519.
One of the greatest puzzles in evolutionary biology is the high frequency of sexual reproduction and recombination. Given that individuals surviving to reproductive age have genomes that function in their current environment, why should they risk shuffling their genes with those of another individual? Mathematical models are especially important in developing predictions about when sex and recombination can evolve, because it is difficult to intuit the outcome of evolution with several interacting genes. Interestingly, theoretical analyses have shown that it is often quite difficult to identify conditions that favour the evolution of high rates of sex and recombination. For example, fitness interactions among genes (epistasis) can favour sex and recombination but only if such interactions are negative, relatively weak and not highly variable. One reason why an answer to the paradox of sex has been so elusive is that our models have focused unduly on populations that are infinite in size, unstructured and isolated from other species. Yet most verbal theories for sex and recombination consider a finite number of genotypes evolving in a biologically and/or physically complex world. Here, we review various hypotheses for why sex and recombination are so prevalent and discuss theoretical results indicating which of these hypotheses is most promising.
进化生物学中最大的谜题之一是有性生殖和基因重组的高频率。鉴于存活至生殖年龄的个体拥有在当前环境中发挥作用的基因组，那么它们为何要冒险与另一个体的基因进行混合呢？数学模型在预测性别和重组何时能够进化方面尤为重要，因为很难凭直觉判断多个相互作用基因的进化结果。有趣的是，理论分析表明，通常很难确定有利于高频率性别和重组进化的条件。例如，基因间的适合度相互作用（上位性）能够促进性别和重组，但前提是这种相互作用为负向、相对较弱且变化不大。性悖论的答案如此难以捉摸的一个原因是，我们的模型过度关注规模无限、无结构且与其他物种隔离的种群。然而，大多数关于性别和重组的文字理论考虑的是在生物和/或物理复杂的世界中进化的有限数量的基因型。在此，我们回顾关于性别和重组为何如此普遍的各种假说，并讨论表明这些假说中哪一个最具前景的理论结果。
