Name ________________________
Honors Monohybrid Cross Homework Problems
Answer the following questions on a separate sheet of paper.
1. Make a list of the seven pairs of contrasting traits Mendel found garden peas to have. State
which is dominant and which is recessive.
2. The gene for black coat color is dominant in guinea pigs. How is homozygous black
different from heterozygous black, even though the guinea pigs look alike?
3. When two hybrid animals are crossed, there appear among the offspring homozygous
dominant, heterozygous and homozygous recessive individuals. Explain.
4. When two parents that are heterozygous for one trait are crossed, what ratio of offspring (F1
generation) is expected to show the dominant trait and what ratio are expected to show the
recessive trait.
5. In guinea pigs, black coat color is dominant over white coat color. What type of offspring
could result from a cross between a homozygous black guinea pig and a heterozygous black
guinea pig? Use a Punnett Square to obtain your results. Include genotype and phenotype
ratios.
6. A pea plant, homozygous for yellow seeds, was crossed with a pea plant homozygous for
green seeds. What is the genotype and phenotype of the F1 and F2 generations?
7. In fruit flies, normal wings are dominant over vestigial wings. What type of offspring could
result from a cross involving a homozygous normal-winged fruit fly and a vestigial-winged
fruit fly? Give the genotype and phenotype ratios.
8. The gene for purple flowers is dominant over the gene for white flowers. What type of
offspring would result from a cross of a purple (homozygous) flowered plant with one
producing white flowers? Give the genotype and phenotype ratios.
9. Mendel crossed a purebred smooth pea, which is dominant, with a purebred wrinkled pea.
Give the results of the F1 and F2 generations. Give the genotype and phenotype ratios.
10. Mendel crossed a hybrid tall pea plant with a hybrid tall pea plant. Give the results of their
offspring. Give the genotype and phenotype ratios.
Pedigree Practice
Incomplete and Codominance Worksheet
Name:
Period:
Date:
Answer the following questions. Provide a punnett square to support your answers where
indicated. Express probabilities as percentages. For instance, a probability of one chance in
ten would be 10%.
(Non-mendelian monohybrid crosses)
1. Explain the difference between incomplete dominance and codominance:
2. In some chickens, the gene for feather color is controlled by codiminance. The allele for black
is B and the allele for white is W. The heterozygous phenotype is known as erminette.
a. What is the genotype for black chickens? ____
b. What is the genotype for white chickens? ____
c. What is the genotype for erminette chickens? ____
3. If two erminette chickens were crossed, what is the probability that:
a. They would have a black chick? ____%
b. They would have a white chick? ____%
Parents: ____ X ____
4. A black chicken and a white chicken are crossed. What is the probability that they will have
erminette chicks? ____%
Parents: ____ X ____
5. In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red
(R) and white (W). The heterozygous genotype is expressed as pink.
a. What is the phenotype of a plant with the genotype RR? ___________
b. What is the phenotype of a plant with the genotype WW? ___________
c. What is the phenotype of a plant with the genotype RW? ___________
6. A pink-flowered plant is crossed with a white-flowered plant. What is the probability of
producing a pink-flowered plant? ____%
Parents: ____ X ____
7. What cross will produce the most pink-flowered plants? Show a punnett square to support
your answer.
Parents: ____ X ____
8. Another type of non-mendelian trait: Multiple alleles. Human hair color is controlled by one
gene
with four alleles (with some incomplete dominance):
HBr = brown HBd = blonde hR = red hbk = black
The possible genotypes and phenotypes:
HBdHBd or HBdhbk = blonde HBdHBr = mousy brown
HBdhR = strawberry blonde HBrHBr or HBr hbk = brown
HBrhR = auburn hRhR or hRhbk = red hbkhbk = black
What do you think your parent’s phenotypes and genotypes for hair color are?
What are your phenotype and genotype for hair color?
If someone with auburn hair has children with someone with red hair (but whose mother had
black hair), what are the genotype and phenotype probabilities for their children?
Name __________________________
Sex-linked Traits
1. Colorblindness is a sex-linked trait. It is carried on the X chromosome. List the genotypes
below for each person listed.
A normal female ______________
A normal male ________________
A carrier female _______________
A colorblind male ______________
A colorblind female ____________
2. Can a male be a carrier for colorblindness? Why or why not?
3. Show the genotype and phenotype ratios possible for the children of a colorblind man and a
carrier woman.
4. Hemophilia is also a sex-linked trait carried on the X-chromosome. Is it possible for a
hemophilic woman to have normal sons? Show a Punnett Square to prove your answer.
Human Blood Types
1. List the four human blood types and the genotypes that go with them.
Type _____ = ______________________
Type _____ = ______________________
Type _____ = ______________________
Type _____ = ______________________
2. Is it possible for a man with Type A blood and a woman with Type B blood to have a child
with Type O blood? Use a Punnett Square to support your answer.
3. An extremely rich elderly couple died in a car accident. They had no known living relatives.
A man shows up claiming to be their long lost son. The elderly couple both had Type AB
blood. The man claiming to be their son has Type O blood. Does this man have a claim to
their fortune? Use a Punnett Square to support your answer.
4. A woman with Type A blood and a man with Type AB blood have a baby. The woman is
suing the man for child support, but he is refusing to pay because he says the baby (who has
Type O blood) is not his. Is he right or should he be paying child support? Use a Punnett
Square to prove your answer.