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Genetics Practice Problems
Study the following genetics problems. Determine the letters that will be used for each gene and then complete
a punnett square. Use this information to answer questions about the offspring in each situation.
1.
In seals, the gene for the length of the whiskers has two versions. The dominant version results in long whiskers and
the recessive version results in short whiskers. Parent 1 is purebred dominant and parent 2 is hybrid
Trait 1: ________________________ Dominant :______________ (
)
Recessive: ______________ (
)
a. What percentage of the offspring will have short whiskers?
b. What percentage of the offspring will have long whiskers?
c. How many of four offspring will be like parent 1?
d. How many of the four offspring will be like parent 2?
e. What kind of cross is this?
2.
purebred
hybrid
mixed
In purple people eaters, having horns is dominant and no horns is recessive. One parent is hybrid for horns and the
other parent has no horns.
Trait 1: ________________________ Dominant :______________ (
)
Recessive: ______________ (
)
a. What are the genotypic ratios of the offspring?
b. What are the phenotypic ratios of the offspring?
c. Give 2 possible parent combinations that would guarantee that all of the
offspring would have horns?
Combination 1: ______ x ______
Combination 2: ______ x ______
d. What kind of cross is this?
3.
purebred
hybrid
mixed
In Humans, tongue rolling is a dominant trait. Both parents are hybrid for tongue rolling.
Trait 1: ________________________ Dominant :______________ (
)
Recessive: ______________ (
)
a. number of children who can roll their tongue ______
b. number of children who can’t roll their tongue ______
c. number of children who have the same genotype as their parents ______
d. number of children who have the same phenotype as their parents ______
e. What kind of cross is this?
purebred
hybrid
mixed
4.
In purple people eaters white fur (albino) is a recessive trait. A female purple people eater is a hybrid; she has
offspring with an albino male people eater.
Trait 1: ________________________ Dominant: ______________ (
)
Recessive: ______________ (
)
a. What percentage of the baby purple people eaters will be purple?
b. What percentage of the baby purple people eaters will be albino?
c. What percentage of the baby purple people eaters will be purebreds?
d. From which parent(s) did the albino babies inherit the albino gene?
5.
What if the male in question 4 had been purebred dominant? Complete a punnett square for this parent combination
and then answer the questions below.
a. What percentage of the baby purple people eaters will be purple?
b. What percentage of the baby purple people eaters will be albino?
c. What percentage of the baby purple people eaters will be hybrids?
d. What kind of cross is this?
6.
purebred
hybrid
mixed
In some types of plants, oval seed shape is dominant over round seed shape. A hybrid oval seed plant is crossed with a
round seed plant.
Trait 1: ________________________ Dominant :______________ (
)
Recessive: ______________ (
)
a. What are the genotypic ratios of the offspring?
b. What are the phenotypic ratios of the offspring?
c. Give 2 possible parent plant combinations that would guarantee that at least
one of the offspring plants would have round seeds ?
Combination 1: ______ x ______
Combination 2: ______ x ______
d. What kind of cross is this?
purebred
hybrid
mixed