Which term describes phenotypic variation that is discrete and falls into observable categories?

Which term describes phenotypic variation that is discrete and falls into observable categories?

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

Answer: (C)

Phenotypic variation that falls into observable categories is best described as qualitative variation. This type of variation yields discrete, indivisible classes—think of traits like blood type or ear lobe attachment—where individuals clearly belong to one category or another without intermediate forms. In contrast, quantitative (continuous) variation shows a spectrum of values (such as height or skin color intensity) influenced by many genes and environmental factors. Pleiotropy, on the other hand, refers to one gene affecting multiple traits, not how a trait is distributed into categories. Therefore, the term that matches discrete, category-based variation is qualitative variation.

Phenotypic variation that falls into observable categories is best described as qualitative variation. This type of variation yields discrete, indivisible classes—think of traits like blood type or ear lobe attachment—where individuals clearly belong to one category or another without intermediate forms. In contrast, quantitative (continuous) variation shows a spectrum of values (such as height or skin color intensity) influenced by many genes and environmental factors. Pleiotropy, on the other hand, refers to one gene affecting multiple traits, not how a trait is distributed into categories. Therefore, the term that matches discrete, category-based variation is qualitative variation.