Question

A man with blue eyes and black hair marries a woman with black eyes and brown hair. A year later they have a child. The child has blue eyes and black hair. If black eyes (B) are dominant over blue eyes (b) and black hair (H) is dominant over brown hair (h), which of the following options correctly predicts the genotype of the child?

• A. bbHh
• B. bbHH
• C. BBHH
• D. BbHh

Answer 1

The correct option is A

bbHh

It’s given that black eye colour (B) is dominant over blue (b). Similarly, black hair colour (H) is dominant over brown (h). So, the desirable genotypes will be:

• Father : bbHh, bbHH (blue eyes black hair)
• Mother : Bbhh or BBhh (black eyes brown hair)
• Child : bbHh or bbHH (blue eyes and black hair)

Since the child has blue eyes, both the alleles obtained from the parents for eye colour should be recessive (b).
So, the mother can have only the Bbhh genotype.
Genotype of mother is homozygous for brown hair colour, the child will inherit one recessive allele (h) for brown hair from her. So, the child can have either bbhh or bbHh.
Hence, the desired genotype of blue eyed, black haired child will be bbHh.