Question

In sheep, eye color is controlled by a single gene with two alleles. When a homozygous brown-eyed sheep is crossed with a homozygous green-eyed sheep, blue-eyed offspring are produced. If the blue-eyed sheep are mated with each other, what percent of their offspring will most likely have brown eyes

Answer 1

Answer:

1/4 or 25%.

Explanation:

It is an example of incomplete dominance which is a form of Non-Mendelian inheritance pattern. In this kind of inheritance, the dominant allele is unable to mask the expression of recessive allele completely so the heterozygous off-springs rather than acquiring dominant phenotype acquire a phenotype which is a blend or we can say intermediate between dominant and recessive phenotype.

Let us suppose homozygous brown-eyed sheep has genotype 'BB' and homozygous green-eyed sheep has genotype 'bb'. Their cross will produce all progeny with 'Bb' genotype which have an intermediate eye color which is blue.

The cross between two blue eyed sheep is depicted as under:

                                    Bb x  Bb

                                 /     \      /    \

Progeny:                BB   Bb  Bb   bb

From the results of cross above, we can easily infer that 1 out of the 4 probable progeny 1 will have brown eyes. So the probability is 1/4 or 25%.