1. A pure-breeding yellow female crossed with a pure-breedingwild-type (pink) male give the following F1:

24 wild-type female
22 yellow male

Male and female F1 were crossed, giving the following F2:

12 wild-type female
13 yellow female
14 wild-type male
12 yellow male

Propose a genetic model to explain these results.

2. In Drosphilia, the allele for red eyes, R, is dominantto the allele for white eye, r. This is a sex-linked trait.Determine the possible genotypic and phenotypic ratios expectedfrom a cross between:

a. a heterozygous female and a red-eyed male
b. a heterozygous female and a white-eyed male
c. a homozygous dominant female and a red-eyed male.
d. a homozygous dominant female and white-eyed male.

3. In humans the allele for normal blood clotting, H, is dominantto the allele for hemophilia, h. This is a sex-linked trait. Awoman with normal blood clotting has four children. They are anormal son, a hemophiliac son, and two normal daughters. The fatherhas normal blood clotting. What is the probable genotype for each member of the family?