Name:___________________________________________

Simple Genetics Practice Problems

1. For each genotype, indicate whether it is heterozygous (HE) or homozygous (HO)

AA ____
Bb ____
Cc ____
Dd ____

Ee ____
ff ____
GG ____
HH ____
Ii ____
Jj ____
kk ____
Ll ____

Mm ____
nn ____
OO ____
Pp ____

2. For each of the genotypes below, determine the phenotype.

Purple flowers are dominant to white.
PP ___________________________
Pp ___________________________
pp ___________________________

Brown eyes are dominant to blue eyes.
BB ___________________________
Bb ___________________________
bb ___________________________

Round seeds are dominant to wrinkled.
RR ___________________________
Rr ___________________________
rr ___________________________

Bobtails are recessive (long tails dominant).
TT ___________________________
Tt ___________________________
tt ___________________________

3. For each phenotype, list the genotypes. (Remember to use the letter of the dominant trait)

lizard

Straight hair is dominant to curly.
____________ straight
____________ straight
____________ curly
Tail spikes are dominant to plain tails.
____________ pointed
____________ pointed
____________ round

4. Set up the square for each of the crosses listed below. The trait being studied is round seeds (dominant) and wrinkled seeds (recessive)

pea pod

Rr x rr

punnett

What percentage of the offspring will be round? _______

Rr x R r

punnett

What percentage of the offspring will be round? _______

RR x Rr

punnett

What percentage of the offspring will be round? ___________


Practice with Crosses. Show all work!

5. A TT (tall) plant is crossed with a tt (short plant).

What percentage of the offspring will be tall? ___________

6. A Tt plant is crossed with a Tt plant.

What percentage of the offspring will be short? ______

7. A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR).

 

What percentage of the offspring will be homozygous (RR)? ____________

8. A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant.

 

What are the genotypes of the parents? __________ x __________

What percentage of the offspring will also be homozygous? _______ What is the genotype of all of the offspring? ______

purple flower

 

9. In pea plants purple flowers are dominant to white flowers.

 

If two white flowered plants are cross, what percentage of their offspring will be white flowered? ______

 

10. A white flowered plant is crossed with a plant that is heterozygous for the trait.

 

What percentage of the offspring will have purple flowers? _____________

 

11. Two plants, both heterozygous for the gene that controls flower color are crossed.

 

What percentage of their offspring will have purple flowers? ______________
What percentage will have white flowers? ___________

guinea pig


12. In guinea pigs, the allele for short hair is dominant.

What genotype would a heterozygous short haired guinea pig have? _______
What genotype would a purebreeding short haired guinea pig have? _______
What genotype would a long haired guinea pig have? ________

Show the cross for two heterozygous guinea pigs.

What percentage of the offspring will have short hair? ________

What percentage of the offspring will have long hair? _______