1. Retinoblastoma is an eye cancer caused by a dominant allele. A normal female and an affected male have four children: one normal and three affected. What is the father's genotype? What are the genotypes of all of the offspring?

2. Phenylketonuria (PKU) is inherited as a recessive disorder in humans. Two unaffected parents have three children, one with PKU. What is the probability the fourth child will have PKU?

3. In a dihybrid cross, four hundred offspring were produced and the offspring were equally divided into four different phenotypic classes. What were the most probable genotypes of the parents? Would you arrive at the same conclusion if there were only four offspring?

4. In the garden pea, Mendel found that Yellow seed color (Y) was dominant to green (y), and Round seed shape (R) was dominant to wrinkled (r).
a. What phenotypic ratios would be expected in the F2 of a cross of homozygous Yellow, Round X homozygous green, rinkled (P1 generation)
b. What is the F2 ratio of Yellow: green and of Round: wrinkled?
c. What Mendelian principle explains the ratios obtained in "b"?

5.
In daisies, yellow petals (Y) are dominant over white petals (y), and Black centers (B) are dominant over orange centers (b). Two plants with Yellow petals and Black centers are crossed, and the following offspring were produced:
45 plants with Yellow petals and Black centers
14 plants with Yellow petals and orange centers
16 plants with white petals and Black centers
5 plants with white petals and orange centers
a. What is the phenotypic ratio of the offspring?
b. What are the genotypes of the parents?
Parent 1 genotype:
Parent 2 genotype: