Define and distinguish epistasis and pleiotropy.

Key Concepts

Epistasis

Epistasis refers to the interaction between genes where the expression of one gene is affected by one or more other genes. This can result in a masking effect, where the phenotypic expression of a gene is suppressed or modified by the presence of another gene. For example, in coat color in mice, one gene may determine the pigment type, while another gene can inhibit the expression of that pigment.

Pleiotropy

Pleiotropy occurs when a single gene influences multiple phenotypic traits. This means that a mutation in one gene can lead to various effects on an organism's phenotype, often affecting different systems or characteristics. An example of pleiotropy is the Marfan syndrome, where a mutation in the FBN1 gene affects connective tissue, leading to symptoms in the skeletal, cardiovascular, and ocular systems.

Distinction between Epistasis and Pleiotropy

The key distinction between epistasis and pleiotropy lies in their effects on gene interactions. Epistasis involves the interaction between multiple genes where one gene's expression is modified by another, while pleiotropy involves a single gene affecting multiple traits. Understanding this difference is crucial for studying genetic interactions and their implications in phenotypic variation.