When populations of microorganisms are subjected to certain nonlethal selections, useful mutants arise among the nongrowing cells whereas useless mutants do not. This phenomenon, known as adaptive, directed, or selection-induced mutation, challenges the long-held belief that mutations only arise at random and without regard for utility. In recent years a growing number of studies have examined adaptive mutation in both bacteria and yeast. Although conflicts and controversies remain, the weight of the evidence indicates that adaptive mutation cannot be explained by trivial artifacts and that nondividing cells accumulate mutations in the absence of genomic replication. Because this process tends to produce only useful mutations, the cells appear to have a mechanism for preventing useless genetic changes from occurring or for eliminating them after they occur. The model that most readily explains the evidence is that cells under stress produce genetic variants continuously and at random, but these variants are immortalized as mutations only if they allow the cell to grow.

中文翻译：

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适应性突变：逆境的用途。


当微生物群体经历某些非致死选择时，非生长细胞中会出现有用的突变体，而无用的突变体则不会。这种现象被称为适应性突变、定向突变或选择诱导突变，它挑战了人们长期以来认为突变只会随机出现且不考虑效用的观点。近年来，越来越多的研究检查了细菌和酵母的适应性突变。尽管冲突和争议仍然存在，但大量证据表明，适应性突变不能用微不足道的人为因素来解释，而且非分裂细胞在没有基因组复制的情况下会积累突变。因为这个过程往往只产生有用的突变，所以细胞似乎有一种机制可以防止无用的基因变化发生或在发生后消除它们。最容易解释证据的模型是，处于压力下的细胞会连续、随机地产生遗传变异，但只有当这些变异允许细胞生长时，它们才会作为突变而永生。