Question

A couple has three children, all of whom have brown eyes and blond hair. Both parents are homozygous for brown eyes (BB), but one is a blond (rr) and the other is a redhead (Rr). What is the probability that their next child will be a brown-eyed redhead? ?

A) 1/ 16
B)1/8
C)1/4
D)1/2
E) 1

Answer 1

The probability that the next child will be a brown-eyed redhead is 1/2, considering that both parents have the dominant allele for brown eyes and one parent is heterozygous for hair color. The correct answer is D)1/2.

Step-by-step explanation:

The question pertains to predicting the inheritance of two separate traits using Mendelian genetics: eye color and hair color. The parents' genotypes for eye color are both homozygous dominant for brown eyes (BB), making brown eyes the expected phenotype for their offspring. For hair color, one parent is homozygous recessive for blond hair (rr) and the other parent is heterozygous with one allele for red hair and one for blond (Rr).

Since all offspring will inherit a 'B' allele from each parent, they will all have brown eyes. The hair color of the offspring depends on the combination of alleles inherited. Since the homozygous blond parent can only contribute 'r' alleles, the possible combinations for the offspring are 'Rr' or 'rr', resulting in either red or blond hair.

To be a redhead, the child must inherit the 'R' allele from the heterozygous parent. The probability of this occurring is 1/2 for any given child. However, since eye color is not variable, we only consider the inheritance of hair color.

Therefore, the probability that the next child will be a brown-eyed redhead is:

1/2 (as there is a 50% chance the child will inherit the 'R' allele for red hair).