Punnett Square Practice Sheet
1. Write the five steps to follow when completing a Punnett square.
a. ___________________________________________________________________
b. ___________________________________________________________________
c. ___________________________________________________________________
d. ___________________________________________________________________
e. ___________________________________________________________________
2. Complete a Punnett square (monohybrid cross) with following genotypes.
Male-Yy
Female-yy
a. What is the phenotypic ratio?
b. What is the genotypic ratio?
3. Complete a Punnett square (monohybrid cross) with following genotypes.
a. Male-bb
b. Female-BB
a. What is the phenotypic ratio?
b. What is the genotypic ratio?
4. Let Y=yellow flowers
y= purple flowers
a. What is the genotype for a homozygous yellow flower?
b. What is the genotype for a purple flower?
c. What is the genotype for a heterozygous yellow flower?
d. What is the genotype for a yellow flower that produced purple offspring?
5. Cross a heterozygous yellow flower with a purple flower.
a. What is the phenotypic ratio?
b. What is the genotypic ratio?
6. Albinism is a recessive condition in which the affected organism is unable to manufacture pigment.
This causes white hair and pink eyes. Cross two heterozygous individuals.
a. What is the phenotypic ratio?
b. What is the genotypic ratio?
c. Can these parents have albino children?
7. In humans unattached ear lobes are dominant to attached ear lobes.
E= unattached
e=attached
If your mother has attached ear lobes, you have attached ear lobes and your brother has unattached ear
lobes.
What is the phenotype of your father?