Punnett Square (And Pedigree) Practice

SCCS Honors BiologyName:

Punnett Square (and Pedigree) Practice Period:Date:

1. In the ABO blood type system, there are three alleles - A and B are dominant, O is

recessive.

a. What pattern of inheritance does this show? ______

b. A woman with Type O blood and a man who is TypeAB have are expecting a child. What are the

possible blood types of the kid? ______

Punnett Square:

c. A baby has type AB blood. His mom has type B blood. What are the possible genotypes of his

father? ______

Punnett Square(s):

2. Hemophilia is a sex-linked, recessive trait, meaning that the allele is carried on the X

chromosome and people with a recessive genotype get the disease. A woman who is

heterozygous for the trait has a child with a man who does not have hemophilia.

Show the Punnett Square:

a. What is the mom’s genotype? ______

b. What is the dad’s genotype? ______

c. What is the mom’s phenotype? ______

d. What is the dad’s phenotype? ______

e. What is the chance that the child will have hemophilia?

f. Assuming the couple has a son, what is the chance he will have hemophilia?

3. Huntington’s disease is a dominant disease. Individuals who are homozygous dominant andheterozygous get the disease, but individuals who are homozygous recessive do not get thedisease.

a. What are the genotypes of people who get Huntington’s disease? ______

b. Both parents are heterozygous for the Huntington’s allele. What is the chance thattheir child will not have Huntington’s disease? ______

(Show the Punnett Square)

c. What does this scenario suggest to you about the relationship between the dominantalleles and most common alleles? (Hint – how many people do you know with Huntington’s) ______

4. Jack and Diane want to have a baby, but both have a history of cystic fibrosis in theirfamilies. Draw a pedigree based on the following information.

- Jack has a brother with cystic fibrosis.

- Jack had a child in a previous marriage that was born with the disease.

- Jack’s parents and sister are all healthy

- Diane is an only child. Her parents are both healthy.

- Diane’s uncle (her mother’s brother) died of cystic fibrosis when he was 3 yrs old

(a. Draw the pedigree)

b. Add genotypes of as many people as possible to the pedigree.

c. You are the genetic counselor that Jack and Diane go to see. What would you tell themabout the chances that their child would have cystic fibrosis? Would you suggest that theytry and have a baby? Or do you think the risks are too high? ______