Question

6. Assume that eye color in humans is controlled by a single pair of genes of which

the effect of that for brown (B) is dominant over the effect of that for blue (b). (a)
What is the genotype of a brown-eyed individual who marries a blue-eyed indi-
vidual and produces a first offspring that is blue-ayed? (b) For the same mating as
in (a), what proportions of the two eye colors are expected among further offspring?
(c) What are the expected proportions of eye colors among the offspring of a mat-
ing between two brown-eyed individuals who each had one parent that was blus-
eyed?

Answer 1

Step-by-step explanation:

(a) The genotype of the brown-eyed individual would be Bb, since they have a dominant B allele for brown eyes and a recessive b allele for blue eyes. The blue-eyed individual would have a genotype of bb.

(b) The offspring of the Bb x bb mating would have a 50% chance of inheriting the b allele from the Bb parent and a 50% chance of inheriting the b allele from the bb parent. Therefore, the expected proportions of the two eye colors among further offspring would be 50% brown-eyed and 50% blue-eyed.

(c) Each of the brown-eyed individuals who had one parent that was blue-eyed would be heterozygous Bb. Therefore, the expected proportions of the offspring's genotypes would be 25% BB, 50% Bb, and 25% bb. Since the B allele is dominant, the expected proportions of eye colors among their offspring would be 75% brown-eyed and 25% blue-eyed.