Question

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

Answer 1

Imagine that there are 5 genes controlling skin color, & the more dominant alleles there are, the darker the skin. AABBCCDDEE would be the genotype for the darkest skin. aabbccddee would be the lightest skin. AaBbCcDdEe would be the most moderate skin color.

Answer 2

Answer;

Polygenic traits are quantitative because their phenotype expression depends on several different alleles found on different chromosomes.

Explanation;

-Using human skin color as an example of polygenic inheritance.

-If we assume that three dominant capital letter genes (A, B and C) control dark pigmentation because more melanin is produced. The recessive alleles of these three genes (a, b & c) control light pigmentation because lower amounts of melanin are produced.

-A genotype with all dominant capital genes (AABBCC) has the maximum amount of melanin and very dark skin. A genotype with all recessive small case genes (aabbcc) has the lowest amount of melanin and very light skin.

-In this case each dominant capital gene produces one unit of skin color, therefore, a wide range of intermediate skin colors are produced depending on the number of dominant capital genes.