Name ___________________________________________
Period ______
Date ______________
Genetics Problems
1. In cabbage butterflies, White wings are dominant to yellow wings. If a heterozygous white
butterfly is crossed with a yellow butterfly, what are the possible genotypes and phenotypes
of the offspring and the percent chance for each?
2. In dogs, there is a hereditary type of deafness caused by a recessive allele. Two dogs who
carry the allele for deafness but have normal hearing are mated. What are the possible
genotypes and phenotypes of their offspring and the percent chance for each?
3. In guinea pigs, short hair is dominant over long hair. If a homozygous short haired guinea pig
is crossed with a long haired guinea pig, what are the possible genotypes and phenotypes of
their offspring and the percent chance of each?
4. Can you curl your tongue up on the sides? Tongue-curling in humans is a dominant genetic
trait. Suppose a man who is heterozygous for tongue-curling marries a woman who is also
heterozygous for this trait. What are the possible genotypes and phenotypes of their children
and the percent chance for each?
5. In guinea pigs, rough coats (with lots of swirly cowlicks) are dominant over smooth coats. If
a homozygous rough guinea pig is crossed with a heterozygous rough guinea pig, what are
the possible genotypes and phenotypes of the offspring? What are the chances of each?
6. Two carnations (flowers), a red one and a white one, are crossed and the F2 offspring have
three different phenotypes.
a. If this gene shows incomplete dominance, what is the color of the heterozygous plants?
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b. If this gene shows codominance, what is the color of the heterozygous plants?
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7. A man with type A blood marries a woman with Type B blood. Their child has Type O blood.
a. What are the genotypes of these individuals? __________________________________
b. What other genotypes and in what frequencies, would you expect in offspring from this
marriage? _____________________________________________________________
8. Color pattern in a species of duck is determined by one gene with three alleles. Alleles H and I
are codominant, and allele i is recessive to both. How many phenotypes are possible in a flock
of ducks that contains all the possible combinations of these three alleles?
9. In dogs, gum coloration is codominant. You have a lovely spotted gummed (black and pink)
Labrador retriever who has just had 8 pups. Four of the pups have spotted gums like your dog,
and 4 have pink gums. What is the likely phenotype of the sneaky neighbor dog?
10. A rooster with gray feathers is mated with a hen of the same phenotype. Among their
offspring, 15 chicks are gray, 6 are black, and 8 are white.
a. What is the simplest explanation for the inheritance of these colors in chickens?
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b. What offspring would you predict from the mating of a gray rooster and a black hen?
____________________________________
11. The base height of the weed is 10 cm. However, the height of weed is the result of polygenic
inheritance involving three genes (A's, B's, C's). Each dominant allele can contribute 5 cm to
the height of the plant. Thus, the homozygous state for a dominant gene can contribute
10 cm to the base height of the plant. This means that a plant that is AABBCC would be
40 cm tall, while aabbcc plant would be 10 cm. tall.
a. If a plant with the genotype (AABBCC) is crossed with a base plant (aabbcc), what
will be the genotype and phenotype (height) of the offspring?
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b. How many phenotypic classes would be present if these offspring were crossbreed?
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12. How many unique gametes can organisms with each of the following genotypes produce?
a. rrss __________________________________________
b. RRss _________________________________________
c. RrSS _________________________________________
d. RrSs _________________________________________
13. In tomato plants, the allele for purple stems (A) is dominant to the allele for green stems (a)
and the allele for red fruit (R) is dominant to the allele for yellow fruit (r). If two tomato
plants heterozygous for both traits are crossed, what proportion of the offspring are expected
to have:
a. purple stems and yellow fruits ____________
b. green stems and red fruits ____________
c. purple stems and red fruits ____________
d. green stems and yellow fruit ____________
14. In tomato plants, what would be the expected genotypic and phenotypic frequencies if a
heterozygous purple stemmed, yellow fruit bearing plant was crossed with a green stemmed,
heterozygous red fruit bearing plant?
15. In some plants, a true-breeding, red-flowered strain gives all pink flowers when crossed with
a white-flowered strain: RR (red) x rr (white) ---> Rr (pink). If flower position (axial or
terminal) is inherited as it is in peas, what will be the ratios of genotypes and phenotypes of
the generation resulting from the following cross: axial-red (true-breeding) x terminal-white?
What will be the ratios in the F2 generation?