1. The ability to taste PTC (phenylthiocaramide) depends on the presence of a dominant gene (T) non-tasters are homozygous for the recessive gene (t). This is a classic case of dominant - recessive inheritance. (a) Consider a mating between heterozygous parents--what proportion of the offspring will be tasters? (b) Consider a mating between Tt and tt parents - what proportion will be homozygous dominant?...what proportion will be non-tasters?

 2. If 2 animals are both heterozygous for a single pair of traits and they produce 200 offspring--about how many would be expected to display the dominant phenotype?

 3. When 2 long-winged flies are mated, the offspring included 75 with long wings and 25 with short ones. Is the short winged condition dominant or recessive? What are the genotypes of the parents?

 4. A color-blind man marries a women with normal vision (remember color blindness is sex-linked). The woman’s father was also color-blind. (a) what is the chance that their first child will be color-blind? (b) What is the chance that their first child will be a color-blind daughter?

 5. A woman with blood type A has two children. One has type O blood and the other has type B blood. What is the mother’s genotype? What is the fathers genotype and phenotype? What are the children’s genotypes?

 6. Most albino children are born to normally pigmented parents. Albinos are homozygous for the recessive gene (aa). What can you conclude about the parents genotype?

 7. A man of blood group A and a woman of blood group B have a child of blood group O. What other genotypes could these parents produce?

 8. A blue-eyed man, both of whose parents were brown-eyed, married a brown eyed woman whose father was blue-eyed and whose mother was brown-eyed. Eye color is a simple dominant recessive trait, with blue being recessive. What are the genotypes of all these individuals?

 9. In rabbits, spotted coat is dominant to solid, and black is dominant to brown. A brown-spotted rabbit is mated to a solid black one, and all the offspring are black-spotted. What are the parents probable genotypes? If two of these black-spotted rabbits were mated what would their offspring look like?

 10. The long hair of Persian cats is recessive to the short hair of Siamese, but the black coat of Persians is dominant to the brown and tan of Siamese. If a pure black, long-haired Persian is mated to a pure brown and tan, short-haired Siamese, what will be the appearance of the first generation? If two of the F-1 are mated, what is the chance of producing a long-haired, brown and tan cat?

 11. One pair of genes for coat color in cat is sex-linked. The gene (B) produces a yellow coat, (b) produces a black coat, and a heterozygote (Bb) has the tortoise-shell pattern of coat color. What kind of offspring result from the mating of a black male and a tortoise-shell female?

 12. Mrs. Doe and Mrs. Roe had babies at the same hospital and at the same time. Mrs. Doe took home a girl and named her Nancy. Mrs. Roe took home a boy and named him Richard, however she was sure she had a girl and sued the hospital. Mr. Roe is type O, Mrs.  Roe is type AB, both the Does are type B. Nancy is type A and Richard is type O. Was their an exchange?

 13. A black guinea pig crossed with an albino one gave 12 black offspring. When the same albino was crossed with a second black one, 7 blacks and 5 albinos were obtained. What are the genotypes for all these guinea pigs (assume a single allele controls coat color)?

 14. In squash an allele for white color (W) is dominant over the allele for yellow color (w). Give the genotype and phenotype ratios for the results of each of the following crosses:

    W/W x w/w
    W/w x w/w
    W/w x W/w

 15. In humans, brown eyes are dominant over blue eyes. Suppose a blue-eyed man marries a brown-eyed woman whose father was blue eyed. What proportion of their offspring would you predict will have blue eyes?

 16. Suppose that an allele, b, of a sex-linked gene is recessive and lethal. A man marries a woman who is heterozygous for this gene. If this couple had a large number of normal children, what would be the expected sex ratio of surviving children?

 17. A rooster with blue (actually gray) feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are blue, 6 are black, and 8 are white. What is the most probable explanation for the inheritance of feather color in chickens? What offspring would you predict from the mating of a blue rooster and a black hen? What offspring would you expect from the mating of a blue hen and a white rooster?

 18. Phenylketonuria (PKU) is an inherited disease determined by a recessive allele. If a woman and her husband are both carriers, what is the probability that their first child will be normal? What is the probability that their first child will be afflicted?