Biology Graded Inheritance homework
Version A
(40 points)
Directions: You must support all answers with a punnett square or some clear explanation for full
credit.
Name:
Date:
1.
PKU stands for phenylketonuria, which is the inability to recognize and process the amino acid
phenylalanine. PKU is an inherited disease caused by a recessive gene. If a mom and a dad are
both carriers for the disease:
a. What is the probability of producing a child with PKU?
b. What is the probability of producing a child that has the gene and can pass it on, but
does not have the disease?
2.
A rooster with blue feathers is bred with a hen with blue feathers. The resulting chick colors are
15 blue, 6 black, and 8 white. The blue color is really a fancy gray and desirable among chicken
breeders.
a. What is the likely inheritance pattern for these color outcomes?
b. What color outcomes would you expect if a blue feathered rooster was bred with a
black feathered hen?
3.
Imagine that you are a genetic counselor. A couple (Henry and Sylvia) are expecting a baby.
Unfortunately, due to multiple complications with the pregnancy, no genetic tests can be done
on the unborn baby or the mother. Henry and his ex-wife have a daughter with cystic fibrosis.
Sylvia had a brother that died of the same disease. Neither Henry nor Sylvia have the disease.
Based on this incomplete information what is the probability that Henry and Sylvia will have a
child with cystic fibrosis?
4.
Green (G) is dominant in peas. Yellow (g) is recessive. What are the genotypes of the P1
generation if the F1 generation is about 75% green and 25% yellow.
5.
Polydactly (extra digits) is a dominant trait. Anne Boleyn, the second wife of Henry VIII had 11
fingers. Anne and Henry only had one child, Elizabeth I, who had the normal number of fingers.
What is the probability that Anne and Henry would have children with extra digits?
6.
Blood types in humans are influenced by two genes, one for ABO immunoglobin and one for the
Rh clotting factor. The immunoglobin gene and the Rh gene are independent of each other (no
epistasis). Type A and type B show no dominance with each other, but both dominate over O.
Having the Rh clotting factor (positive) is dominant to not having it (negative).
Dad has type O positive blood and Mom has type AB positive blood. They have fraternal twins one has A
negative blood and one has B positive blood. Explain how it is possible for children to have blood types
that that neither of their parent have.
7.
A species of rabbit can be black, white, or spotted. When a male black rabbit is bred with a
female white rabbit the bunnies are black and white spotted. Explain this pattern of inheritance
8.
Colorblindness is a sex-linked trait located on the X chromosome. If dad is colorblind and mom
does not have any genes for colorblindness, what are the probabilities of producing a colorblind
son? What about a colorblind daughter?