Punnett Square Practice Sheet #2
Use page 77 to complete the following questions.
1. Cross a plant that is heterozygous for axial flowers with a plant that has terminal flowers.
a. What is the phenotypic ratio? _______________________
b. What is the genotypic ratio?_________________________
2. Cross a homozygous tall plant with a short plant.
a. What is the phenotypic ratio?__________________________
b. What is the genotypic ratio?____________________________
3. Three-fourths of the plants produced by a cross between two unknown pea plants have axial flowers and
one-fourth have terminal flowers.
a. What are the genotypes of the parent plants?__________________
b. What are the phenotypes of the parent plants?_________________
4. Determine the genotype and phenotype of a cross that would result in ½ of the offspring having green pods
and ½ having yellow pods?
Genotypes- ♂_________________♀_______________
Phenotypes- ♂_________________♀_______________
5. Let B = Brown hair and b = blonde hair
a. What is the genotype for hair in a person who is homozygous dominant?______________________
b. What is the phenotype of a person who is homozygous dominant for hair color?_________________
c. What is the genotype for hair in a homozygous recessive person?____________________________
d. What is the phenotype of a person who is homozygous recessive for hair color?_________________
e. What is the genotype for hair in a heterozygous person?___________________________________
f. What is the phenotype of a person who is heterozygous for hair color?________________________
g. What is the genotype for a person with brown hair who has a son with blonde hair?______________
h. What is the genotype for the spouse of the person above if they have brown hair?_______________
i. What is the genotype for a person with blonde hair?______________________________________
6. Tay Sachs’ disease is a recessive condition in which the affected person has loss of motor skills, paralysis
and mental retardation. Cross two heterozygous individuals.
a. What is the phenotypic ratio?___________________
b. What is the genotypic ratio?____________________
c. What is the probability that these parents are going to have a child with Tay Sach’s?_____________
d. What is the probability that these parents are going to have a child that is a carrier of Tay Sach’s?
________________________________________________________
7. In humans unattached ear lobes are dominant to attached ear lobes.
E= unattached
e=attached
Your mother has attached ear lobes, you have attached ear lobes and your brother has attached ear lobes.
a. What is the genotype of your father?____________________
b. What is the phenotype of your father?___________________