Question

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

Explanation:

Polygenic traits are influenced by multiple genes. Skin color is a polygenic trait. Multiple genes contribute to the production of melanin (the pigment responsible for skin color). Different combinations of alleles (gene variants) from these multiple genes result in a wide range of skin colors (quantitative variation). For example, if there are three genes (A - a, B - b, C - c) contributing to skin color, a person with genotype \(AABBCC\) may have very dark skin, while a person with \(aabbcc\) may have very light skin, and many intermediate genotypes (\(AaBbCc\), \(AABbcc\) etc.) lead to various shades in - between.

Answer:

Polygenic traits are expressed through quantitative variation (like skin color) because multiple genes contribute to the trait. Each gene has alleles that can add to or subtract from the phenotype. For skin color, multiple genes control melanin production. Different combinations of alleles from these genes result in a continuous range of skin colors (from very light to very dark with many intermediate shades), which is an example of quantitative variation for a polygenic trait.