1. Color blindness is a sex-linked disease (B = normal, b = color-blind). A color-blind male has children by a normal female. They have a color-blind son and a normal daughter. Indicate the genotypes of the parents and the offspring.

If the above daughter later had a son of her own, what are the chances that the son would be normal?

2. What is the difference between maternal inheritance and the inheritance of a sex-linked trait?

3. If the litter resulting from the mating of two short-tailed cats contains three kittens without tails, two with long tails, and six with short tails, what would be the simplest way of explaining the inheritance of tail length in these cats? Show genotypes.

4. The "a" locus in maize affects anthocyanin biosynthesis such that colored kernels result when plants contain one or more dominant alleles of the a locus. Another gene "sh" affects starch biosynthesis in the kernel. Plants homozygous for the recessive allele of sh produce kernels that are collapsed or shrunken, like a raisin. The genes for a and sh are on chromosomes 4 and 9, respectively. If a plant heterozgyous for seed color and seed shape is self pollinated and one ear from this plant produces 496 kernels;

5. A human disease called pseudohypertrophic muscular dystrophy is inherited as a sex-linked recessive trait. The disease is characterized by a wasting away of the muscles, beginning about age 6, so that by the time affected persons are in their teens they usually die before reaching adulthood. If a woman, who came from a family where one of her two brothers died from the disease, were to marry and have children, will her sons likely suffer the fate of her diseased brother? What is the probability that her surviving brother will have a son afflicted by the disease?

6. A plant breeding true for fully colored flowers was crossed with a plant true breeding for white flowers. The F1 progeny all had fully colored flowers. When the F1 were crossed among themselves, they produced 81 plants with fully colored flowers and 63 white-flowered plants. When the F1 plants were backcrossed to the white-flowered parent, 78 plants had white flowers and 24 had colored flowers. What is the explanation for these results? (hint: coloration in plants is often controlled by more than one gene).