Components of means: additive and dominance effects

Abstract

In diploid organisms the individual can fall into any one of three genetic classes (AA, Aa and aa) in respect of a gene for which there exists two alleles (A and a). The effect of the gene difference on the phenotype can be described by two parameters and specified completely if the values of these two parameters are known. In the system adopted by Fisher, Immer and Tedin (1932) and Mather (1949a) one parameter (d) is used to represent the phenotypic difference between the two homozygotes AA and aa and the other (A) to represent the departure in phenotype of the heterozygote Aa from the mid-point between AA and aa (m).