Definition of Muller's ratchet in English:

Muller's ratchet

Pronunciation /ˌmʊləz ˈratʃɪt/


(also Muller's Ratchet)
  • A hypothetical mechanism having the effect of invariably increasing the number of harmful mutations in a population of asexually reproducing organisms, since genotypes with the fewest harmful mutations will be among those lost at random in an irreversible manner (likened to a ratchet).

    The mechanism was proposed to account for the existence of sexual reproduction, which permits the restoration of favourable genotypes by genetic recombination.


1970s; earliest use found in Genetics. From the genitive of the name of Hermann Joseph Muller, U.S. geneticist, who proposed the theory in 1964 (Mutation Res 1 2) + ratchet.