Final answer:
Epistasis is the term used to describe the situation where a gene controls both seed coat color and susceptibility to a particular disease. This is a common occurrence in genetics, where multiple genes interact to influence the expression of observable characteristics. It helps explain why a single gene does not always have complete control over a particular trait.
Step-by-step explanation:
The situation described, where a gene controls both seed coat color and susceptibility to a particular disease, is an example of epistasis in biology. Epistasis refers to the interaction between multiple genes where the expression of one gene masks or modifies the expression of another gene. In this case, the gene controlling seed coat color is also affecting the plant's susceptibility to a disease.
Epistasis is a common occurrence in genetics, and it helps explain why the expression of a single observable characteristic is often influenced by multiple genes. Genes work together in complex networks, and their interactions can have a significant impact on an organism's phenotype.