1. A homozygous recessive genotype for the gene that encodes phenylalanine hydroxylase (which breaks down the amino acid phenylalanine) causes lighter skin color, a musty odor, differences in intellectual development, and seizures. 2. In pea plants, alleles of Gene W control flower color, with the dominant allele (W) leading to purple flower.color, and the recessive allele (w) leading to white flower color. Usually, a genotype of WW or Ww leads to purple flowers. However, when Gene C is homozygous recessive, WW or Ww plants always have white flowers. 3. In mallard ducks, feather coloring is controlled by Gene F. A dominant allele (F) leads to head feathers, while a recessive allele (f) leads to brown head feathers. In male green mallards, inheritance of one or more F alleles always leads to the green head feather trait. But female mallards always have brown head feathers, regardless of whether they are FF, Ff, or ff.

4. A man and woman marry and have 3 children. When the man is 50 years old, he is diagnosed with Huntington's disease (which is inherited dominantly). The woman is tested and she does not carry the gene. What is the chance for each child to have Huntington's disease? Are the 3 events (the children having HD) independent or mutually exclusive? What are the chances that all three children are HD free? If one of the three children marries a person with no family history of HD (assume normal), what is the chance that their child will have the disease? (we do not know yet if the parent has it or not)

5. What are the genotypes of individuals in the following autosomal recessive trait, attached earlobe? A Ww ww B A. What is the genotype of individual C3? B. Individuals B4 & B5 are going to have another child. What is the probability that their next child will have an attached earlobe? C. How many children A1 has?

5. Flower color in snapdragons is inherited in an incompletely dominant manner. Assume that RR = red flowers, Rr = pink flowers, and rr = white flowers. What would be the genotype and phenotype ratios of the offspring of two plants with pink flowers?