Uploaded by Cora Da Costa Pereira

Practicing Punnett Squares and Pedigrees

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Practicing Punnett Squares and Pedigrees
Directions: Answer the following questions on a piece of binder paper. Be sure to show Punnett
squares and pedigrees (including genotypes) to prove your answers.
Case Study: Sickle Cell Anemia
Sickle­cell anemia is known to be a hereditary disease. It has a pattern of inheritance that closely
follows the model for recessive traits described by early geneticist Gregor Mendel. For a recessive
trait to appear, a person must have inherited two copies of the recessive gene.
1. John and his wife Anna are heterozygous for Sickle­cell. Create a Punnett Square to analyze the
odds of any offspring inheriting sickle­cell anemia.
2. If their child who has both normal hemoglobin genes marries a person who has sickle­cell
anemia, what is the probability of any of their offspring inheriting sickle­cell anemia (use a
Punnett square)?
3. If a person has anemia, his or her blood cells are oxygen deprived. Describe to this couple how
a person with sickle­cell anemia might feel.
4. Why would simple blood transfusions not be able to cure this disease?
5. Make a Pedigree of John and Anna’s family. They have one non sickle­cell son who married a
normal female. However the son has an infected daughter. Show all genotypes.
Punnett Squares and Pedigrees: Why Do I (or don’t I) Have Freckles and Curly Hair?
Solve the genetics problems below by using Punnett squares and pedigrees. Write your answers on a
separate piece of paper.
The gene for freckles has two alleles.
F =freckles (dominant allele)
f=no freckles (recessive allele)
1. a. Dan is heterozygous for freckles. His wife, Deborah, does not have any freckle. Create a
Punnett square to predict the results of their children.
b. What percentage of their children will have freckles?
c. What percentage of their children will not have freckles?
d. Make a pedigree of Dan’s family if he had 3 sonsÍž the oldest has freckles, the others do not.
2. a. Sara and Justin both have freckles and both are heterozygous for this trait. Create a Punnett
square to predict the results of their children.
b. What are the chances they will have a child with freckles?
c. What is the chance they will have a child with the FF genetic makeup?
d. Make a pedigree for Sara, Justin, and both their parents. Justin’s mom and Sara’s dad both
have freckles.
3. a. Make a pedigree for YOUR family’s freckles genes. Include your parents and siblings.
b. Include all genotypes.
The gene for hairstyle has two alleles.
H= curly hair (dominant allele)
h= straight hair (recessive allele)
4. Gloria has straight hair and her husband, Andre, also has straight hair. Make a pedigree of their
family, which includes 2 girls and a boy. The boy is the youngest. Don’t forget genotypes.
5. Make a pedigree for Maria’s familyÍž Maria has straight hair. Her mother, Irma, has curly hair and
her father, Pedro, also has curly hair. Maria has an older sister with curly hair, but who has a
straight haired son. Maria also has a younger brother with straight hair, whose daughter has curly
hair. Maria has 2 children, a son with curly hair, and a daughter with straight.
6. a. Do you have curly hair or straight hair? What is your genotype?
b. Make a pedigree of your immediate family (parents and siblings) to determine your genotype.
Include all family members’ genotype.
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