Question

In humans, having a widow's peak is the result of a dominant gene, and having a normal hairline is a recessive trait. A man who has a widow's peak is homozygous for the trait and has a child with a woman who has a normal hairline. Which of the following best describes the most likely appearance of their child's hairline?

Answer 1

Without knowing what options you have to chose from, all we can is general help.

The first thing to do is come up with some letters to represent the genes and alleles. Let's call it w, lower case, for the recessive normal hairline and upper case W for the dominant widow's peak.

You are told that the man has a widow's peak - so you know he must have at least one dominant W allele. You are also told that he is homozygous, meaning both his alleles are the same. So you know his genotype is WW.

You are told that the woman does not have a widow's peak - and this only happens when she has only recessive alleles. So her genotype is ww.

You set up your Punnett Square:

Answer 2

Filling in the Punnett Square gives you the kids' genotypes, which should give you a lot of info about whatever question you have to answer on this cross.