Assessment

1. What fraction of plants in Mendel's second experiment would be homozygous short?

2. What fraction of plants would be homozygous tall?

3. What fraction would be heterozygous?

4. If one hundred offspring were produced, how many would you expect to be tall?

Now, let us consider an example of a human trait. The presence of a widow's peak hairline is determined by a dominant and recessive gene. A widow's peak is a "v" shaped hairline. The trait for widow's peak is dominant W, and no widow's peak is recessive w.

Widow's Peak

Complete the Punnett square to show the possible outcomes of a cross of a heterozygous father with a widow's peak with a homozygous mother with a widows's peak.

What fraction of offspring would have a widow's peak?

What fraction of offspring would not have a widow's peak?