Two models of the evolution of gene families on the Y chromosome under concerted evolution. The length of the branches shown is proportional to ratio. (a) When gene conversion does not increase the fixation rate of beneficial mutations in multigene families, the rate of evolution is reduced compared to that of single-copy gene because gene conversion is expected to reduce the fixation rate of deleterious mutations. (b) When gene conversion increases the fixation rate of beneficial mutations in multigene families, the rate of evolution is higher compared to single-copy genes.
