Genetics Problems
1.) A white (true breeding) rat is mated with a black (true breeding) rat (P 1). All the offspring are
black (F1).
a.) Which trait is dominant, white or black?
The F1 generation is allowed to interbreed.
b.) Give the expected genotypic and phenotypic ratios of the F2 offspring, drawing Punnett
Squares for the F1 and F2 generations to back up your answer. (Be sure to identify your
alleles by giving a key)
c.) What is the expected percentage of offspring in the F2 generation that will be white?
2.) You cross a female that is AABB and a male that is Aabb.
a.) What gamates will the female produce?
b.) What gametes will the male produce?
c.) Show with a Punnett Square, the percentage of offspring from these parents that will be
AaBb?
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3.) In sheep, white wool (W) is completely dominant over black wool (w). A white ram is bred to
another white sheep. They produce both white and black lambs. What are the genotypes of the ram
and his mate and why?
4.) What would be the expected blood types of children produced from the following matings?
a.) O x Homozygous A
b.) AB x AB
c.) Heterozygous A x Homozygous B
d.) Could a Type A man and a Type B woman have a Type O child? Could a Type AB man
and a Type B woman have a Type O child? Demonstrate your answers with Punnett
Squares.
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5.) You want to grow a garden of only tall pea plants. You know the allele for tall pea plants is
dominant over the allele for dwarf pea plants. You are given a random tall pea plant to start your
garden. How can you determine if your tall pea plant is true breeding? Name the procedure and
diagram a Punnett Square outlining your procedure.
6.) You want to self pollinate a pea plant that has the following genotype: AaBb.
a.) What are the possible gametes produced by this plant?
b.) Fill in a Punnett Square for a mating of AaBb x AaBb
7.) Ragweed hay fever is a disorder caused by a dominant allele. If a man with hay fever (whose
mother did not have hay fever) mates with a woman without hay fever,
a.) What is the genotype of the man?
b.) What are the chances their children will be afflicted?
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8.) In a paternity case, both mother and child have blood type O. The suspected father has blood
type B.
a.) Knowing just this, could he be the father of the child? Why or why not?
Additional tests show that the suspected father’s parents are both Type AB.
b.) Can you tell now if he is the father? Show Punnett Squares to prove your answer.
9.) In peas, tall plants (T) are dominant over short plants (t). The gene for smooth seeds (S) is
dominant over wrinkled seeds (s). You cross the following individuals:
(male) ttSs x (female) Ttss
a.) What gametes will the male produce?
b.) What gametes will the female produce?
c.) What is the genotypic ratio of their offspring Show the Punnett Square.
d.) What is the phenotypic ratio of their offspring?
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