What type of traits do polygenic traits often exhibit?

• A. Discrete and clear-cut phenotypes
• B. Complex and continuous variation
• C. Only dominant traits
• D. Only traits affected by environmental conditions

Answer: (B)

Polygenic traits are those that are influenced by multiple genes, each contributing to the overall phenotype in varying degrees. This genetic complexity results in traits that show a range of variations rather than distinct categories. Because more than one gene is involved, the effects of these genes can accumulate, leading to continuous variation in the phenotypes.

For example, human height is a classic example of a polygenic trait. It is not simply categorized as tall or short, but rather individuals can fall anywhere along a spectrum of heights, demonstrating the continuous variation that polygenic inheritance produces. This variation can be graphically represented as a bell curve when you plot the distribution of traits in a population.

In contrast, discrete traits are those that exhibit clear-cut phenotypes, like a flower being either red or white, which are not typical of polygenic traits. The notion of only dominant traits or traits strictly influenced by environmental conditions does not capture the essence of polygenic traits as they often include both dominant and recessive alleles contributing to the overall phenotype, as well as being subject to environmental influences.