Both Jim and his mother have a widow's peak but his father doesn't. Jim marries Lisa, who doesn't have a widow's peak. What is the probability that their children will have widow's peak?

To determine the probability that Jim and Lisa's children will have a widow's peak, we need to consider the genetic factors involved.

In this scenario, both Jim and his mother have a widow's peak, indicating that they carry the dominant allele for this trait. However, Jim's father does not have a widow's peak, suggesting he carries the recessive allele for this trait.

Since both Jim and his mother have the trait, we can infer that Jim is heterozygous for the widow's peak, meaning he carries both the dominant and recessive alleles (Ww). On the other hand, Lisa does not have a widow's peak, which indicates that she does not carry the dominant allele (ww).

Let's assess the possible combinations of alleles that their children can inherit:

1. If Jim passes on the W allele (dominant) and Lisa passes on the w allele (recessive), the child will have a widow's peak (Ww).
2. If Jim passes on the w allele (recessive) and Lisa passes on the w allele (recessive), the child will not have a widow's peak (ww).

Considering these possibilities, there is a 50% chance that each child will have a widow's peak.

It's important to note that this calculation assumes simple Mendelian genetics and only considers the widow's peak trait. Other genetic factors and traits can influence the outcome as well.