Selective sweep

In genetics, a selective sweep is the reduction or elimination of variation among the nucleotides near a mutation in DNA. It results from a beneficial allele having recently reached fixation due to strong positive natural selection. In genetics, a selective sweep is the reduction or elimination of variation among the nucleotides near a mutation in DNA. It results from a beneficial allele having recently reached fixation due to strong positive natural selection. A selective sweep can occur when a rare or previously non-existing allele that increases the fitness of the carrier (relative to other members of the population) increases rapidly in frequency due to natural selection. As the prevalence of such a beneficial allele increases, genetic variants that happen to be present on the genomic background (the DNA neighborhood) of the beneficial allele will also become more prevalent. This is called genetic hitchhiking. A selective sweep due to a strongly selected allele, which arose on a single genomic background therefore results in a region of the genome with a large reduction of genetic variation in that chromosome region. The idea that strong positive selection could reduce nearby genetic variation due to hitchhiking was proposed by John Maynard-Smith and John Haigh in 1974.