Molecular drive

Molecular drive is a term coined by Gabriel Dover in 1982 to describe evolutionary processes that change the genetic composition of a population through DNA turnover mechanisms. Molecular drive operates independently of natural selection and genetic drift.

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The best-known such process is the concerted evolution of genes present in many tandem copies (multigene families), such as those for ribosomal RNAs or silk moth egg shell chorion proteins, in sexually reproducing species. The mechanisms involved include gene conversion, unequal crossing-over, transposition, slippage replication and RNA-mediated exchanges. Because mutations changing the sequence of one copy are less common than deletions, duplications and replacement of one copy by another, the copies gradually come to resemble each other much more than they would if they had been evolving independently.

Concerted evolution can be unbiased, in which case every version has an equal probability of being the one that replaces the others. However, if the molecular events have any bias favouring one version of the sequence over others, that version will dominate the process and eventually replace the others. The name 'molecular drive' reflects the similarity of the process with what was originally the better-known process of meiotic drive.

Molecular drive can also act in bacteria, where parasexual processes such as natural transformation cause DNA turnover.

Key paper

• Dover GA (1982) Molecular drive: A cohesive mode of species evolution. Nature 299: 111–7.

Review

• Dover GA (1986) Molecular drive in multigene families: how biological novelties arise, spread and are assimilated. Trends Genet. 159-65.