Which condition involves a single gene affecting multiple traits?

Pleiotropy is a condition in which a single gene influences multiple phenotypic traits. This occurs because a single gene product can have various effects on different biological pathways or developmental processes. For example, the gene responsible for certain metabolic disorders may affect not only one aspect of metabolism but also lead to multiple symptoms affecting different organ systems, such as neurological issues, growth abnormalities, and skin problems.

In contrast, epistasis describes the situation where the expression of one gene is affected by one or more other genes. Codominance occurs when two different alleles of a gene are both expressed in the phenotype, leading to a situation where both traits are visible, such as in the case of certain blood types. Sex-linkage refers to traits that are linked to sex chromosomes, often affecting the expression of traits differently in males and females. Each of these concepts highlights different aspects of genetic interaction and inheritance, making pleiotropy distinct in its definition of a single gene influencing multiple traits.