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.

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