Question

A widow's peak is more dominant than a straight hairline.

What is the likelihood of having children with the same phenotype as their father if a mother is heterozygous for the widows peak gene and a father has a straight hairline?

A. 0

B. 0.25

C. 0.5

D. 1

Answer 1

Remember that a dominant gene will always be expressed, even if there is only one copy of the gene. A recessive gene will only be expressed if there are two copies of the gene.

Complete step-by-step Answer:

The mother has one copy of the dominant widow's peak gene (W) and one copy of the recessive straight hairline gene (w). The father has two copies of the recessive straight hairline gene (ww).

When the mother and father have children, there are four possible outcomes for each child:

• The child receives one copy of the widow's peak gene from the mother and one copy of the straight hairline gene from the father. The child will have a widow's peak.

• The child receives one copy of the widow's peak gene from the mother and one copy of the straight hairline gene from the father. The child will have a widow's peak.

• The child receives one copy of the straight hairline gene from the mother and one copy of the straight hairline gene from the father. The child will have a straight hairline.

• The child receives one copy of the straight hairline gene from the mother and one copy of the straight hairline gene from the father. The child will have a straight hairline.

The probability that a mother heterozygous for the widow's peak gene and a father with a straight hairline would have children with the same phenotype as their father is 0.5. Therefore, there is a 50% chance that any child of this couple will have a straight hairline.

Hence the correct answer is Option C

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Note:

This question is based on the concept of incomplete dominance, which is a type of inheritance in which neither allele is completely dominant or recessive. In incomplete dominance, the heterozygous phenotype is somewhere between the two homozygous phenotypes.