Multiple effects of a single gene is known as

Multiple effects of a single gene are known as Pleiotropy.
It describes the genetic effect of a single gene on multiple phenotypic traits. The underlying mechanism is genes that code for a product that is either used by various cells or has a cascade-like signaling function that affects various targets.
Pleiotropy means that a single gene affects two or more characters. It is a single gene that affects the fitness of the organism at two or more ages. It is convenient to categorize the combinations of age-specific pleiotropic effects.