Question

In a three-gene polygenic cross involving skin colour with genes A/a, B/b, and C/c, what does the capital letter (A, B, C) represent?

Options

• Non-contributing alleles that produce lighter skin colour

• Contributing alleles that produce darker skin colour

• Genes that are linked on the same chromosome

• Recessive alleles that mask dominant traits

Answer 1

In the polygenic inheritance model for human skin colour, capital letters (A, B, C) represent contributing alleles that add to darker pigmentation, while lowercase letters (a, b, c) represent non-contributing alleles that result in lighter skin colour. Each contributing allele contributes equally and additively to the final phenotype.