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 flowers |
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 |
Pointed heads are dominant
to round heads. ____________ 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? ______________
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? ________
13. Show the cross for a pure breeding
short haired guinea pig
and a long haired guinea pig.
What percentage of the offspring will have short hair? __________
14. 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? _______
15. Two short haired guinea pigs
are mated several times. Out of 100
offspring, 25 of them have long hair. What are the probable
genotypes of the parents? ________ x ___________ Show the cross to prove it!
