Interaction between different genes residing within the same genome in the production of a particular phenotype. Such interactions often occur when the products of the nonallelic genes under study function at steps in a sequence of reactions that result in compounds which generate the phenotype in question. These interactions can produce variations from the classical genetic ratios. An example would be the inheritance of aleurone color in Zea mays. In order for the corn kernel to possess colored aleurone, at least one A and one C gene must be present. Given A and C in the heterozygous or homozygous condition and, in addition, R in the heterozygous or homozygous condition, then a red pigment is produced. Purple pigment is synthesized if P is present in addition to A, C, and R. All four genes reside on different chromosomes. Thus, if a plant of genotype AaCCRRPp is self-pollinated, the offspring will contain the following aleurone classes: purple, red, and white in a 9:3:4 ratio. Here the 9:3:3:1 ratio has been converted into a 9:3:4 ratio, because the P gene cannot be expressed in the absence of A.
Subjects: Genetics and Genomics.