Question

A brown-eyed couple has a blue-eyed child. The trait of brown eye (B) is dominant over that of blue-eyed (b). What is the genotype of the couple?

• A. Bb $\times$ Bb
• B. BB $\times$ BB
• C. BB $\times$ Bb
• D. BB $\times$ bb

Answer 1

Answer: (A)

Bb $\times$ Bb

• B is the dominant gene for the brown colored eye. So, for the progeny to be blue-eyes the recessive allele needs to be inherited from both the parents. This means, the brown-eyed parents need to be heterozygous.
• The genotype of the couple is Bb x Bb because only this combination can give 25% probability of bb genotype in progeny which accounts for blue eyes.

So, the correct answer is 'A'.