Question

In humans, the allele for brown eyes is dominant to the allele for blue eyes. If a man with blue eyes (bb) and a woman with brown eyes (BB) who is homozygous for eye color have children, what is the probability of having a child with blue eyes?

A. 25 percent
B. 100 percent
C. 50 percent
D. 0 percent

Answer 1

The man has the genotype of bb, meaning he has two copies of the recessive blue eye allele. The woman has the genotype of BB, meaning she has two copies of the dominant brown eye allele. Therefore, all their children will inherit one copy of the brown eye allele from the mother (B) and one copy of the blue eye allele from the father (b).
Since brown eyes are dominant, any individual with at least one copy of the brown eye allele will express that trait. Therefore, all the children will have brown eyes, and the probability of having a child with blue eyes is 0 percent (D).
The genotype of the children will be Bb, meaning they are heterozygous for eye color. However, they will still express the dominant brown eye trait because they have at least one copy of the brown eye allele.

Answer 2

The probability of a child having blue eyes from this particular parent combination would be 0 percent, since the man has the genotype bb, which means that he can only pass the b allele to his children. The woman is homozygous for brown eyes (BB), which means that she can only pass the B allele to her children.

Therefore, all of the children of this couple will be heterozygous for eye color (Bb) and have brown eyes. To summarize, the answer is D, 0 percent probability.