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Question

Question
Blonde hair (b) is recessive, and brown hair (B) is dominant.

A parent has brown hair (Bb). Their first child has blonde hair (bb). Their second child has brown hair (BB).

What must the other parent have (hair color and allele combination)?

(1 point)
Responses

BB, brown hair
BB, brown hair

Bb, brown hair
Bb, brown hair

Bb, blonde hair
Bb, blonde hair

bb, blonde hair
bb, blonde hair
Remaining Attempts : 3
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Answer 1

To determine the hair color and allele combination of the other parent, let's analyze the genetic information provided:

• The first parent has brown hair with a genotype of Bb (heterozygous for brown hair).
• The first child with blonde hair has a genotype of bb (homozygous recessive).
• The second child with brown hair has a genotype of BB (homozygous dominant).

For the blonde-haired child (bb) to arise, they must inherit one recessive allele (b) from each parent. Since the first parent is Bb, they can provide one b allele. Therefore, the other parent must also provide a recessive b allele.

Since one child is BB and another is bb, this means the second parent cannot possibly be BB since they cannot contribute a b allele to the first child.

Thus, the possible genotypes of the second parent must be Bb (heterozygous) or bb (homozygous recessive), but since one child has brown hair (BB), the only suitable combination of alleles for the other parent that allows for a child with blonde hair while also being able to produce a brown-haired child is Bb.

Therefore, the answer is:

Bb, brown hair