**Pleiotropy** is best described as:
- Two genes controlling one trait
- One gene controlling two or more different traits
- Two pairs of contrasting alleles
- Multiple alleles at a single locus
Show answer and solution
Correct answer: B. One gene controlling two or more different traits
A pleiotropic gene controls multiple, apparently unrelated traits.
Sickle-cell anaemia is a classic example — the Hb^s allele causes anaemia, organ damage, AND confers malaria resistance.
Multiple alleles is a distinct concept (different versions of one gene).