Which statement describes a quantitative trait?

• A. A trait with continuous variation such as height.
• B. A trait with discrete categories such as blood type.
• C. A trait determined by a single gene with two alleles.
• D. A trait that is not heritable.

Answer: (A)

A quantitative trait is one that shows continuous variation across individuals, not broken into separate categories. Height is a classic example because people fall along a spectrum from shorter to taller with many intermediate sizes rather than just tall or short. This smooth range occurs because many genes contribute to height (polygenic) and environmental factors like nutrition also influence the final size, producing a normal-looking distribution of phenotypes.

In contrast, a trait with discrete categories, such as blood type, is qualitative because individuals group into a few distinct classes rather than a continuous spectrum. A trait determined by a single gene with two alleles tends to produce a limited number of phenotypes, again not a continuous range. A trait that is not heritable wouldn’t be genetic and thus wouldn’t show genetic variation across individuals.

So the statement describing continuous variation such as height best captures a quantitative trait.