Which genetic concept explains why a single gene can influence multiple phenotypic traits?

Which genetic concept explains why a single gene can influence multiple phenotypic traits?

• A. Polygenic traits
• B. Qualitative variation
• C. Quantitative variation
• D. Pleiotropy

Answer: (D)

Pleiotropy is the idea that one gene can influence multiple phenotypic traits because its product participates in several different biological processes or affects multiple tissues. This means a single genetic change can ripple through an organism, producing effects in several traits at once. A classic example is the sickle cell gene, where a mutation in the beta-globin gene alters red blood cell shape and function, and this single change also influences other health aspects and, in some contexts, malaria susceptibility. The other terms describe how traits are inherited or expressed: polygenic traits involve many genes shaping one trait (like height), while qualitative and quantitative variation refer to how a trait is observed across individuals, not to how many traits a single gene can affect.

Pleiotropy is the idea that one gene can influence multiple phenotypic traits because its product participates in several different biological processes or affects multiple tissues. This means a single genetic change can ripple through an organism, producing effects in several traits at once. A classic example is the sickle cell gene, where a mutation in the beta-globin gene alters red blood cell shape and function, and this single change also influences other health aspects and, in some contexts, malaria susceptibility. The other terms describe how traits are inherited or expressed: polygenic traits involve many genes shaping one trait (like height), while qualitative and quantitative variation refer to how a trait is observed across individuals, not to how many traits a single gene can affect.