What genetic phenomenon occurs when a single gene influences multiple, seemingly unrelated traits?

Pleiotropy is the correct answer because it describes the situation where one single gene affects multiple traits that may seem unrelated. This phenomenon is a fundamental concept in genetics and helps explain various biological processes, including certain genetic disorders. A classic example of pleiotropy is the gene responsible for cystic fibrosis, which impacts several different bodily systems, including the lungs and digestive tract.

In contrast, polygenic inheritance involves multiple genes contributing to a single trait, exemplified by traits like height or skin color, where many genes work together to produce a range of phenotypes. Epistasis refers to the interaction between genes, where one gene can mask or modify the expression of another, affecting the trait outcome but not necessarily causing multiple unrelated traits to be influenced. The concept of multiple alleles refers to the existence of more than two alleles for a genetic trait, such as the ABO blood group system, but does not address the interaction of a single gene influencing various traits.