Explain why polygenic traits are expressed through quantitative variation, using skin color as an example.

Answer 1

Polygenic traits are traits that are controlled by multiple genes, each with a small effect on the overall phenotype. This means that the expression of the trait is not simply determined by a single gene with dominant and recessive alleles, but rather by the combined effects of multiple genes.

One example of a polygenic trait is skin color. Skin color is determined by multiple genes that control the production of melanin, a pigment that gives skin its color. Each gene contributes a small amount to the overall amount of melanin produced, resulting in a range of skin colors in human populations.

Because skin color is a polygenic trait, it is expressed through quantitative variation. This means that individuals can fall anywhere along a spectrum of skin colors, rather than fitting into discrete categories. For example, someone with very dark skin may have inherited more of the genes that promote the production of melanin, while someone with very light skin may have inherited fewer of these genes.

The variation in skin color seen in human populations is a result of the complex interactions between multiple genes, as well as environmental factors such as sun exposure. This makes skin color a good example of a polygenic trait that is expressed through quantitative variation.