有限的基因组大小可以阻止穆勒的棘轮
Finite genome size can halt Muller's ratchet
摘要：
我们研究了有害突变的积累，在一个单倍体，无性繁殖的人口，使用分析模型和计算机模拟。我们发现，穆勒的棘轮可以停止在小群体中作为一个有限的基因组大小的结果，在完全没有向后或补偿突变，上位性，或重组。这种效应的起源在于这样一个事实，即突变可以产生相当大的损害的位点数量随着棘轮的每一次转动而减少，而每个基因组和每一代的突变总数保持不变。棘轮最终是否会停止取决于每个位点的有害突变率$u$和选择强度$s$的比率。对于足够小的$u/s$，棘轮在发出几声咔嗒声后停止。我们讨论了我们的研究结果对细菌和病毒进化的影响。
英文摘要：
We study the accumulation of deleterious mutations in a haploid, asexually reproducing population, using analytical models and computer simulations. We find that Muller's ratchet can come to a halt in small populations as a consequence of a finite genome size only, in the complete absence of backward or compensatory mutations, epistasis, or recombination. The origin of this effect lies in the fact that the number of loci at which mutations can create considerable damage decreases with every turn of the ratchet, while the total number of mutations per genome and generation remains constant. Whether the ratchet will come to a halt eventually depends on the ratio of the per-locus deleterious mutation rate $u$ and the selection strength $s$. For sufficiently small $u/s$, the ratchet halts after only a few clicks. We discuss the implications of our results for bacterial and virus evolution.
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