The authors note that the citation of Wright (1937) and Nei (1968) is incorrect in the “Models of mutation-selection balance” section in Results. Wright (1937) not only showed the equilibrium frequency of a deleterious allele for a population of infinite size (Eq 1) but also derived the full equilibrium frequency distribution of a deleterious allele under a finite effective population size. He also derived the mean (Eq 2) allele frequency of a fully recessive deleterious allele and gave approximations for large and small effective population sizes. Nei (1968) further derived the approximate variance (Eq 3) in allele frequency of a fully recessive mutation by using Wright’s general formula. The authors confirm that this error does not affect the conclusions of the article.