Index >> Quantitative genetics (Inheritance of Multiple Genes) >> Modifying Factors

Modifying Factors
The inheritance of certain traits is governed by a single pair of genes which determines the presence or absence of the trait plus a number of multiple genes which determine the extent of the trait. For example, the presence or absence of spotted coat in most mammals is determined by a single pair of genes. The gene for the presence of spots (s) is recessive to the gene for the solid colour (S). The size and distribution of the spots is determined by a series of polygenes called modifying factors. A modifying polygene, thus, affect the degree of expression of another gene.