Name ______________________________________ Date _________________________ Period ___________
Punnett Square Practice
Define the following terms and give an example.
 Homozygous
 Heterozygous
 Phenotype
 Genotype
 Dominant
 Recessive
On the line next to each genotype, write HOM if it is homozygous or HET if it is
heterozygous.
1. Dd __________________
6. HH __________________
2. TT __________________
7. Pp __________________
3. Rr __________________
8. MM __________________
4. aa __________________
9. Qq ___________________
5. Yy __________________
10. ii ___________________
For each Punnett Square problem, write the parent genotypes. Then fill out
the Punnett Square and write the genotype and phenotype probabilities for
the offspring.
1. In rabbits, black fur (B) is dominant over white fur (b). Show the cross of a
heterozygous black male with a homozygous white female.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
What is the probability of…
 The offspring having black fur? __________________
 The offspring having white fur? __________________
 The offspring being homozygous dominant? __________________
 The offspring being heterozygous? __________________
2. Tall (T) is dominant over short (t) in pea plants. Show the cross of a
homozygous short plant is crossed with a homozygous tall plant.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
What is the probability of…
 The offspring being tall? _________________
 The offspring being short? _________________
 The offspring being homozygous dominant? _______________
 The offspring being homozygous recessive? ________________
 The offspring being heterozygous? __________________
3. In humans, free-ear lobes (F) are dominant to attached (f). Two parented
that are both heterozygous free are expecting a child. What are the chances
that the child will have free ear lobes of attached?
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
What is the probability of….
 The offspring having free-ear lobes? _________________
 The offspring having attached ear lobes? _________________
 The offspring being homozygous dominant? _______________
 The offspring being homozygous recessive? ________________
 The offspring being heterozygous? __________________
4. Wrinkled seed are recessive to smooth seeds. Show a plant that always
produces wrinkled seeds crossed with a heterozygous smooth seeds
producing plant.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
What is the probability…
 The offspring having wrinkled seeds? _________________
 The offspring having round seeds? _________________
 The offspring being homozygous dominant? _______________
 The offspring being homozygous recessive? ________________
 The offspring being heterozygous? __________________
5. Blue eyes (B) are dominant to red eyes (b) in rabbits. Show a heterozygous
blue-eyed rabbit crossed with a red-eyed rabbit?
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
What is the probability…
 The offspring having blue eyes? _________________
 The offspring having red eyes? _________________
 The offspring being homozygous dominant? _______________
 The offspring being homozygous recessive? ________________
 The offspring being heterozygous? __________________
6. In fruit flies, red eyes (R) are dominant over white eyes (r). Show a cross
between two white-eye fruit flies.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
Incomplete Dominance and Codominance. Use your textbook to write the
definitions.
 Incomplete Dominance
 Codominance
For each Punnett Square problem, write the parent genotypes. Then fill out
the Punnett Square and write the genotype and phenotype probabilities for
the offspring.
1. In four o’clock plants, red flowers (R) are incompletely dominant over white
flowers (W). Heterozygous plants show a blended intermediate phenotype
of pink flowers.
Make a cross between two heterozygous four o’clock plants.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
2. Make a cross between a homozygous red four o’clock plant and a
homozygous white four o’clock plant.
Parent Genotypes: _____________ and ______________
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________
3. In the ABO blood type system the A and B alleles are DOMINANT to the O allele and
A and B are CO-DOMINANT with each other.
Make a cross between a man with AB genotype and a woman with BO genotype.
Offspring Genotypes
_______________________
_______________________
_______________________
_______________________
Offspring Phenotypes
_______________________
_______________________
_______________________
_______________________