Selective sweeps for recessive alleles and for other modes of dominance

TL;DR

This paper extends the theory of selective sweeps by analyzing the effects of different dominance modes, especially recessive alleles, on genetic diversity patterns and sweep duration.

Contribution

It introduces a generalized model for selective sweeps with any dominance coefficient and characterizes the unique dynamics of recessive beneficial alleles.

Findings

Genetic diversity patterns under recessive sweeps differ significantly from other modes.

Sweep duration for recessive alleles scales with the square root of population size over selection strength.

Recessive beneficial alleles have a distinct impact on genetic variation compared to co-dominant alleles.

Abstract

A selective sweep describes the reduction of linked genetic variation due to strong positive selection. If s is the fitness advantage of a homozygote for the beneficial allele and h its dominance coefficient, it is usually assumed that h=1/2, i.e. the beneficial allele is co-dominant. We complement existing theory for selective sweeps by assuming that h is any value in [0,1]. We show that genetic diversity patters under selective sweeps with strength s and dominance 0<h<1 are similar to co-dominant sweeps with selection strength 2hs. Moreover, we focus on the case h=0 of a completely recessive beneficial allele. We find that the length of the sweep, i.e. the time from occurrence until fixation of the beneficial allele, is of the order of sqrt(N/s) generations, if N is the population size. Simulations as well as our results show that genetic diversity patterns in the recessive case h=0 greatly differ from all other cases.