Which term describes a trait controlled by genes on the sex chromosomes?

• A. Sex linked trait
• B. Test cross
• C. Polygenic trait
• D. Incomplete dominance

Answer: (A)

Sex-linked trait describes a trait controlled by genes on the sex chromosomes. In many species, those genes are on the X chromosome, and because males have only one X, a recessive allele on that chromosome is often expressed in males, while females would need two copies to show the trait. This distinctive inheritance pattern is what makes the term sex-linked the correct description for a trait tied to the sex chromosomes. The other terms don’t fit: a test cross is used to infer genotype, a polygenic trait involves many genes, and incomplete dominance is about how heterozygotes express a blend of parental traits, not about the trait’s location on sex chromosomes.