Answer :But what happens when two different loci affect the same characteristic? For instance, what if both of the loci in Mendel's experiment affected seed color? When two genes are involved in the outcome of one characteristic, a dihybrid cross involving these genes can produce a phenotypic ratio very different from 9:3:3:1. Under these circumstances, there are more than two gene products affecting the same phenotype, and these products may have complex hierarchical relationships. Any time two different genes contribute to a single phenotype and their effects are not merely additive, those genes are said to be epistatic.
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