Muller's ratchet

In evolutionary genetics, Muller's ratchet (named after Hermann Joseph Muller and a mechanical device) is the name given to the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner.

Muller proposed this mechanism as a theory to explain the evolution of sex. One must note, that although Muller's ratchet is proposed to explain the success of sexual reproduction over asexual reproduction, the effect may not[clarify] be prevalent in organisms that reproduce asexually but undergo other forms of recombination and may be observed in the portions of the genomes of organisms that reproduce sexually which do not undergo recombination.