Abstract
When the various genotypes (A(i)A(i), A(i)A(i)) of an autosomal locus do not reproduce and contribute equally to the genetic composition of the next generation, we say that the "fitness" values of the genotypes are different, or that there is natural selection on the genotypes. Under natural selection, the average fitness for a random mating population increases with time until a stationary state is reached. This communication gives a general expression for the amount of increase of the average fitness per generation of selection. It was found that the amount of increase depends largely on the linear or additive component of the variance of the genotype fitness values and, to a lesser extent, on the dominance pattern for the values of heterozygote fitness relative to those of homozygote fitness.