Permanent Cause of Genetic Correlation

Correct Answer: Pleiotropy

From the notes: Pleiotropy is the permanent cause of genetic correlation. A pleiotropic gene by definition controls multiple traits — so the correlation between those traits is a permanent feature of the genome and cannot be broken by breeding.

Contrast with Linkage

• Pleiotropy: Permanent — because the same gene physically controls both traits. No breeding method can separate the effects.
• Linkage: Transient/temporary — because crossing over can recombine the linked genes over generations, gradually breaking the correlation.

Pleiotropic Examples (from notes)

• Sickle cell anemia gene: affects RBC shape, oxygen transport, malaria resistance
• Halothane gene in pigs: affects stress response, meat quality (PSE pork), reproductive traits
• Double muscling gene in cattle: affects muscle mass, fat deposition, calving difficulty, fertility