Genetics Problems 3
1. An individual male fruit fly was discovered that had a bluish cast to its body. When it was bred with a scarlet-eyed female, all the F1 females had the blue body color, and all of the F1 males were entirely normal. Remember that only the mutant (= unusual )traits are mentioned; if a trait is normal, it is not specified.
a. Are the mutations (blue body and scarlet eyes) autosomal or X-linked?blue body
scarlet eyes
b. Are the mutations dominant or recessive?
blue body
scarlet eyes
c. What are the genotype of the parents?
blue-bodied male
scarlet-eyed female
d. What would be the expected phenotypic ratio in the male and female F2 offspring if the F1 progeny were intercrossed?
2. A child with type O blood questions whether she was adopted. Her father's blood is type A, her mother's is type B. What can she conclude from this information?
3. A true-breeding female fruit fly with a yellow body (rather than the normal grey body) was crossed with a true-breeding male with wrinkled wings. The F1 female progeny all had wrinkled wings and the F1 male progeny all had yellow bodies and wrinkled wings.
a. Are yellow body and wrinkled wings dominant or recessive?yellow body
wrinkled wings
b. Are yellow body and wrinkled wings autosomal or X-linked?
yellow body
wrinkled wings
c. What are the genotypes of the parents?
yellow-bodied female
wrinkled-winged male
d. If you intercrossed the F1 progeny, what phenotypes and ratio would you expect among the F2's?
4. A rare human trait is phenylketonuria, or PKU. People with PKU cannot properly metabolize the amino acid phenylalanine. The phenylalanine builds up in their tissues and causes mental retardation and physical developmental abnormalities. Fortunately, the symptoms can be prevented by maintaining phenylketonurics on a low phenylalanine diet starting within a few days of birth. That's why there is a national PKU screening program for all newborns. Given that a phenylketonuric can be born to two normal parents, what is the mode of transmission? Consider autosomal vs. X-linked and dominant vs. recessive.
5. The black and yellow pigments in the coats of cats is controlled by an X-linked pair of alleles. Females heterozygous for these alleles have areas of black and areas of yellow in their coat (called "calico").
a. A calico cat has a litter of eight kittens -- one yellow male; two black males; two yellow females; and three calico females. Assuming there is a single father for the litter, what is his probable color?
b. A yellow cat has a litter of four kittens -- one yellow and three calico. Assuming there is a single father for the litter, what is the probable sex of the yellow kitten?
6. A true-breeding purple-eyed female fruit fly was crossed with a true-breeding black-bodied male. The F1 progeny were all normal for both traits. The F2 phenotypic ratios differed between males and females as shown below.
|
females: |
3/4 normal : |
1/4 purple-eyed |
||
|
males: |
3/8 normal : |
3/8 yellow-bodied : |
1/8 purple-eyed : |
1/8 purple-eyed and yellow bodied |
Diagram this cross, showing the genotypes for the parents, the F1's and each of the F2 phenotypes.
7. Pedigree problems
What is the most likely mode of inheritance for each of the following RARE traits?
