GENE INTERACTIONS (POST MENDELIAN GENETICS)

Phenotypic expression of a gene may be altered by the influence of other genes. The modification of the normal phenotype of certain genes by other genes is known as gene interaction.

The gene interaction is of 2 types : intragenic or interallelic and intergenic or nonallelic.

1. Intragenic Interactions

These interactions occur between the two alleles of same gene to produce a phenotype different from the normal dominant - recessive phenotype. The common intragenic interactions are incomplete dominance, codominance, multiple alleles.

2. Intergenic Interactions

These interactions occur between the alleles of different genes present on the same or different chromosomes to alter the normal phenotype. The familiar intergenic interactions include complementary genes, supplementary genes, polygenes, epistasis, pleiotropy, lethal genes etc.