Intragenic Gene Interactions

Intragenic (intra-allelic, or intralocus) gene interactions take place between the different alleles of the same gene, at the same chromosomal locus. Four patterns fall under this heading: incomplete dominance, in which neither allele is fully dominant and the heterozygote shows an intermediate phenotype; codominance, in which both alleles are expressed together, side by side, in the heterozygote; multiple alleles, where more than two allelic forms of a gene exist in the population even though any one individual carries only two of them; and pleiotropy, where a single gene's alleles influence several apparently unrelated traits at once. The next few sections work through incomplete dominance, codominance and pleiotropy in detail with worked …