Selective Sweep

Sweeps can be categorized in three main categories.

  1. The “classic selective sweep” or “hard selective sweep” is expected to occur when beneficial mutations are rare, but once a beneficial mutation has occurred it increases in frequency rapidly, thereby drastically reducing genetic variation in the population.
  2. A so-called “soft sweep from standing genetic variation” occurs when a previously neutral mutation that was present in a population becomes beneficial because of an environmental change. Such a mutation may be present on several genomic backgrounds so that when it rapidly increases in frequency, it doesn’t erase all genetic variation in the population.
  3. Finally, a “multiple origin soft sweep” occurs when mutations are common (for example in a large population) so that the same or similar beneficial mutations occurs on different genomic backgrounds such that no single genomic background can hitchhike to high frequency.

Genetic terminology

  1. genetic hitchhiking: 遗传搭车
  2. singleton: SNP’s shared by more than one individual indicate levels of relatedness, while SNP’s found only within one individual, referred to as “singletons”, indicate uniqueness.