Pleiotropy refers to?

• A. A gene affecting only one trait
• B. A gene affecting more than one trait
• C. A trait affecting multiple genes
• D. A gene that has no effect on phenotype

Answer: (B)

Pleiotropy means a single gene influences more than one trait. This happens because the gene’s product can participate in multiple cellular processes or be active in several tissues, so a mutation can ripple through different parts of the organism.

A classic example is a gene mutation that affects connective tissue in multiple systems, leading to effects on height, joints, and heart or eye structures. Another example is a gene variant in hemoglobin that changes red blood cell shape and also causes pain, organ damage, and other health issues in sickle-cell disease.

This differs from a situation where many genes influence one trait (polygenic inheritance) or from a gene that only affects a single trait, or from a gene that has no effect on phenotype.