A stochastic model concerning the maintenance of genetic variability in quantitative characters.

Abstract

A new model was proposed to explain the maintenance of genetic variability in quantitative characters. The model assumes that at every locus involved with the quantitative character, mutation can produce an infinite sequence of alleles and the effect of a new allele is only slightly different from the parental allele from which it was derived by a single mutational step. The new model is in sharp contrast with the conventional models in which mutation is assumed to occur only between a pair of alleles, say A or a. Together with the additional assumptions that the genes are additive with respect to the quantitative character, that the optimum phenotype is fixed, and that fitness decreases in proportion to the squared deviation from the optimum, the properties of the model were worked out, enabling one to make predictions about the relation between mutation rates, genotypic variance, and mutational load.