Interaction and linkage

Abstract

The contributions to the genetic variation of gene pairs at different loci are additive, in the way assumed in the previous chapter, only if the genes at the various loci are independent in both action and inheritance. Independence in action means, of course, that the increment added to the character in question by the substitution of one allele for another at a given locus is uninfluenced by the remaining genes under consideration. Independence in inheritance means that the two alleles at one locus are equally likely to be transmitted from parent to offspring together with a given allele at the second locus. Apart from special cases, therefore, dependence of genes in inheritance means linkage. We will consider the consequences for the components of variation of these two kinds of dependence in turn.