Question

For a particular gene that determines the coat color in a diploid organism, there are three different alleles that are co-dominant. How many different skin colors are possible in such an organism?

• A. $9$
• B. $6$
• C. $4$
• D. $3$

Answer 1

The correct option is B $6$

Skin colour is a good example of polygenic (multiple genes) inheritances. Skin colour is determined by the amount of the dark colour pigment melanin in the skin. This trait is determined by at least three genes. The genes that determine skin colour have two alleles each and are found on different chromosomes.

For example, three genes that are known to influence skin colour, each gene has one allele for dark skin colour and one for light skin colour. The allele for dark skin colour (D) is dominant to the allele for light skin colour (d). Skin colour is determined by the number of dark alleles a person has. Individuals who inherit no dark alleles will have very light skin colour, while those that inherit only dark alleles will have very dark skin colour. Individuals who inherit different combinations of light and dark alleles will have phenotypes of varying skin shades.

Hence, with 3 genes for skin colour and each gene having 2 alleles, the number of skin colours possible = 3*2= 6

So, the answer is B.