Download Punnett Square Problems

Honors Biology: Punnett Square Problems #3
Name
Date
Instructions: Use Punnett squares to answer the following questions, as you did with the previous Punnett
square worksheet (review that for help).
Complete this assignment working by yourself.
Working together in any way is not acceptable.
1. Show the Punnett Square and resulting phenotype ratios for a cross of a heterozygous pea plant with
yellow seeds with a plant with green seeds. Yellow pea seeds (Y) are dominant over green pea seeds (y).
Phenotype ratios:
2. Albinism (lack of pigmentation) is due to a recessive allele of a gene that codes for pigmentation (a).
Humans who have at least one copy of the dominant allele (A) have pigmentation (are not “albino”). A man
with albinism marries a normal woman whose father had albinism. What is the chance that they will have a
child with albinism? Show the Punnett Square.
Chance they will have a child with albinism ________
3. How many purple-flowered green-seeded plants will be produced if a heterozygous purple-flowered
homozygous green-seeded pea plant and a pea plant that is homozygous purple-flowered and
heterozygous yellow-seeded are crossed and produce 32 total offspring pea plants? Show the Punnett
Square.
Number of purple-flowered green-seeded plants ___________ (out of 32)
4. Sickle cell anemia is a trait that exhibits incomplete dominance. A person with an AA genotype does not
have sickle cell anemia, and a person with an SS genotype has full sickle cell anemia. A person with an AS
genotype will have some sickle-cells, though s/he might show minimal or no symptoms (a “carrier”).
Julio has full sickle-cell anemia, and his wife, Anne, has some symptoms. What are the chances that Julio
and Anne will have a child with full sickle cell anemia? Show your work!
Percent chance children would have kids with full sickle-cell anemia________________
5. In cows, the allele for red hair (HR) and the allele for white hair (HW) are codominant. The heterozygous
condition results in a mixture of red and white hairs and the cows are called roan. What phenotypes of cows
could be produced if a white cow was crossed with a red cow? Show the Punnett square.
Phenotypes of cows that could be produced: ______________________
6. Human blood type is determined by a gene with THREE alleles. The IA allele produces A proteins on red
blood cells, and is codominant with the IB allele, which produces B proteins. The i allele is recessive and
does not produce any proteins (two recessive alleles results in the “O” blood type).
a. If a woman who is heterozygous for the A blood type and a man who is homozygous for the B blood
type have children, how likely is it that they will produce children with A blood type? Show the
Punnett square.
Chance of producing children with A blood type: __________________
b. A man has the A blood type. His mom has the A blood type and his dad has the B blood type. Can
you determine the genotype of his dad? Can you determine the genotype of his mom? Explain your
reasoning for each.