Simple Genetics Practice Problems
1. For each genotype, indicate whether it is heterozygous (HE) or homozygous (HO)
|
AA ____ |
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. |
Brown eyes are dominant to
blue eyes. BB ___________________________ Bb ___________________________ bb ___________________________ |
|
Round seeds are dominant
to wrinkled. |
Bobtails are recessive (long
tails dominant). |
3. For each phenotype, list the genotypes. (Remember to use the letter of the dominant trait)
| 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)
Rr x rr
What percentage of the offspring will be round? _______
Rr x R r
What percentage of the offspring will be round? _______
RR x Rr
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? ______
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? ___________
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? _______
Other Resources on Genetics
Peas, Please – practice setting up squares for basic Mendelian traits in pea plants (Key, TpT)
Practice Punnett Squares with Skinny Pigs – hairless guinea pigs are the result of a recessive gene (Key, TpT)
Fruit Fly Genetics (Vg) – practice worksheet on vestigial wing flies (recessive trait)
Explore the Genetics of Corn Snakes – dihybrid crosses with corn snakes, color is polygenic