Name: ______Date: ______
Pedigree Practice Problems
Section 1: Pattern of Inheritance is Given to you
1. The pedigree below shows the family members that are able to roll their tongue, which is a dominant trait over those who cannot roll their tongue.
a. Can you determine the genotypes of the two parents? If so, write them in on the lines and explain how you knew them. If not, explain why you can’t determine what they are.
b. Write in as much of the genotypes of the children that you know. Explain why you did or did not know what the genotype was.
2. The pedigree below shows the incidence of red green colorblindness within a family. Red green colorblindness is a recessive, sex-linked disorder.
a. Write in the genotype of the female in the original P generation (I).
How do you know this?
b. What are the possible genotypes for
all of the daughters in the F1 generation (II)?
c. Write in all the genotypes for the F2 generation (III).
3. The pedigree below shows a family with 3 children. The mom has type AB blood. The first daughter is homozygous for type B blood and the second daughter is heterozygous for type B blood. The son has type A blood.
a. Using the proper notation, which includes the Roman numeral for the generation and the number of the individual (ex: II – 2), write down which family members have which blood types.
Type A:
Type B:
Type AB:
Type O:
b. Write in the genotypes of each individual in the pedigree above or below their symbol.
4. The trait shaded in the following pedigree is inherited as an autosomal recessive trait with the alleles T and t.
a. What is the chance that individual II-1 is heterozygous for the trait?
b. What is the chance that individual II-3 is homozygous for the trait?
c. What is the chance that individual III-3 has the genotype TT?
d. If individual III-1 marries a male heterozygous for the trait, what is the chance that their first child will show the trait?
Part 2: The Pattern of Inheritance is NOT Given
1. Use the pedigree below to answer the questions that follow. All individuals with a particular trait are shaded in.
a. Is this trait in the pedigree a dominant or recessive trait? How do you know?
b. Is this trait in the pedigree sex-linked or autosomal? How do you know?
c. Which individuals (include Roman numeral & number) would have to be carriers?
2. In the pedigree below, individuals that are shaded in have a particular trait.
a. What is the mode of inheritance for this trait? (Your options are autosomal dominant, autosomal recessive, sex-linked dominant, or sex-linked recessive). Explain how you chose your answer.
b. What are the genotypes for the following individuals:
I-1: ______II-2: ______II-3: ______
II-4: ______II-5: ______II-6: ______
III-1: ______III-2:______III-6:______
Part 3: Constructing a Pedigree
1. Use the information below to create a pedigree and then answer the question at the end of the description.
A man and woman marry. They have five children: a girl, 3 boys, and another girl. The mother is a carrier of hemophilia, which is a recessive, sex-linked disease. She passes the gene on to two of the boys who died in childhood. Her first daughter is also a carrier. Both daughters marry men without hemophilia and have 3 children (2 boys and a girl). The carrier daughter has one son with hemophilia. One of the non carrier daughter’s sons marries a woman who is a carrier and they have twin daughters. What is the percent chance that each daughter will also be a carrier?