Name: __________________________________________________________ Date: _____________
Genetics Practice Problems
Period: ___________
PROBLEMS
1. In humans, free earlobes (E) are dominant over attached earlobes (e). A heterozygous free earlobed male
marries a female with attached earlobes. What will be the possible phenotype and genotype of the
offspring?
50% Free 50% Attached
50% Ee 50% ee
2. Using the information given in #1, cross two heterozygous free ear lobed parents and give the genotype
and the phenotype of their possible offspring.
25% Attached 75% Free
25% EE 50% Ee 25% ee
3. If all the offspring of a particular set of parents has Tt for their genotype, what is the genotype of the
parents?
TT and tt
4. In watermelons, solid green (G) color is dominant over striped pattern (g), and short shape (S) is
dominant over long shape (s). What is the genotype and phenotype of all the possible offspring if you
cross a homozygous green, heterozygous short watermelon with a heterozygous green, long watermelon?
GGSs X Ggss
¼ GGSs ¼ GGss ¼ GgSs ¼ Ggss
½ Green and short ½ Green and long
5. Incomplete dominance may be observed in short-tailed cats (TNTL). The absence of the long tail gene
results in a manx cat (no tail TNTL). The absence of a no tail gene results in a long tail cat (TLTL). What
would be the genotype and the phenotype of the possible offspring if you cross two short tail cats?
25 % No Tail
50 % Short Tail
25% Long Tail
TNTL
TNTL
TLTL
6. A man is colorblind with the genotype Xc Y. The mother is not colorblind but carries a colorblind allele.
Give all the possible genotypes and phenotypes.
25% XC Xc Normal Girl
25% Xc Y Colorblind Boy
25% XC Y Normal Boy
25% Xc Xc Colorblind Girl
7. Suppose a person with type A blood and a person with type B blood get married. What are the possible
genotypes their children could have? Show all possible crosses.
AO X BO
AA X BO
AO X BB
AA X BB
25% AB
25% AO
25% BO
25% OO
50% AB
50% AO
50% AB
50% BO
100% AB
8. A black cat breeds with a tan cat and their kittens are all black-and-tan tabby (striped or mottled) cats.
Set up a Punnet square that shows how this could happen. Is this incomplete dominance or codominance?
R’ R’
R RR’ RR’
R
RR’ RR’
Co-dominance
9. If two black-and-tan tabby cats, with genotypes that are like the kittens in problem 3, are bred, what are
the odds of any one of their kittens being tabby? All black? All tan?
Tabby 50%
Black 25%
Tan 25%
10. A purebreeding red-flowered Four-o’clock (rr) is crossed with a purebreeding white-flowered Fouro’clock (ww). What colors will be seen in the resulting offspring? What will their genotypes be? What
type of inheritance?
Rw 100% Pink
Incomplete dominance
11. If two offspring from the above cross are crossed with each other, what colors will be seen in the
resulting offspring? What will be the genotypes of the resulting offspring?
25% White (ww)
50% pink (rw)
25% red (rr)