High School

In humans, a widow's peak hairline (W) is completely dominant to a straight hairline (m). A woman who is homozygous dominant for a widow's peak mates with a man who is homozygous recessive for a widow's peak. What is the genotype of each parent?

A) Female = WW, Male = WW
B) Female = WW, Male = ww
C) Female = WW, Male = WW
D) Female = ww, Male = WW

Answer :

In this genetics problem, we're dealing with two traits: widow's peak hairline, which is dominant, and straight hairline, which is recessive.

  1. Understanding the Traits:

    • Widow's peak hairline is represented by the allele 'W' and is dominant. This means that having at least one 'W' allele will result in a widow's peak.
    • Straight hairline is represented by the allele 'w' and is recessive, meaning an individual must have two 'w' alleles (ww) to have a straight hairline.

  2. Identifying Parental Genotypes:

    • The woman is described as homozygous dominant for a widow's peak. Homozygous dominant means she has two dominant alleles, so her genotype is 'WW'.
    • The man is described as homozygous recessive for a widow's peak. Homozygous recessive means he has two copies of the recessive allele, so his genotype is 'ww'.

  3. Conclusion:

    • Female = WW
    • Male = ww

In genetic terms, when a woman with the genotype WW mates with a man with the genotype ww, all their offspring will inherit one 'W' from the mother and one 'w' from the father, resulting in the genotype 'Ww'. All offspring will have a widow's peak because 'W' (widow's peak) is dominant over 'w' (straight hairline).

Thus, the correct option is B) Female = WW, Male = ww.

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