In the context of traits and variance, which statement best distinguishes a single-gene (Mendelian) trait from a polygenic trait?

• A. Polygenic traits are controlled by one gene with many alleles, whereas single-gene traits are controlled by many genes with two alleles each.
• B. Single-gene traits typically show discrete phenotypic categories, whereas polygenic traits usually show continuous variation due to the additive effects of many genes.
• C. Single-gene traits always have higher heritability than polygenic traits because environmental effects are negligible for Mendelian traits.
• D. Polygenic traits cannot be influenced by the environment, whereas single-gene traits are strongly influenced by environmental variation.

Answer: (B)