Question

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

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

Answer 1

The correct option is D

bbHh

It’s given that black eye colour is dominant over blue. So we can assign
B to black and b to blue. Similarly, black hair colour (H) is dominant
over brown (h). Based on this we can represent the cross as follows.
$$\begin{array}{cccc}& \text{Male}& & \text{Female}\\ \text{Phenotype:}& \text{Blue eyes and black hair}& & \text{black eyes and brown hair}\\ \text{Genotype:}& \text{bbHH/bbHh}& & \text{Bbhh}\\ \text{Gametes:}& \text{bH bh}& \text{X}& \text{Bh bh}\\ \text{Possible offsprings:}& \text{BbHh bbHh}& & \text{Bbhh bbhh}\end{array}$$

As the child has blue eyes and black hair, the only possible option among the
possible offsprings with this combination is bbHh.