Patterns of Inheritance Worksheet
Name: ________________________
1. Complete the following monohybrid cross. The P generation is true breeding. Cross a plant that
produces yellow seeds with a plant that produces green seeds. Yellow is dominant. Use Y for yellow, y
for green.
P generation phenotype:
genotype:
yellow seeds
green seeds
gametes produced:
F1 generation phenotype:
genotype:
gametes produced:
F2 generation (cross F1 with F1)
Possible phenotypes:
Ratios:
Possible genotypes:
Ratios:
______________________________________________________________________________
2. Complete the following monohybrid cross. The P generation is true breeding. Cross a tall plant with
a short plant. Tall is dominant. Use T for tall, t for short
P generation phenotype:
genotype:
tall
short
gametes produced:
F1 generation phenotype:
genotype:
gametes produced:
F2 generation (cross F1 with F1)
Possible phenotypes:
Ratios:
Possible genotypes:
Ratios:
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3. Complete the following dihybrid cross for seed pod traits. Assume the genes are linked. Green is
dominant. Use G for green, g for yellow. Inflated is dominant. Use I for inflated, i for constricted.
P generation phenotype:
genotype:
yellow constricted pod
green inflated pod
gametes produced:
F1 generation phenotype:
genotype:
gametes produced:
F2 generation (cross F1 with F1)
Possible phenotypes:
Ratios:
Possible genotypes:
Ratios:
__________________________________________________________________________________
4. Complete the following dihybrid cross for seed pod traits. Assume the genes are NOT linked.
Green is dominant. Use G for green, g for yellow. Inflated is dominant. Use I for inflated, i for
constricted.
P generation phenotype:
genotype:
yellow constricted pod
gametes produced:
F1 generation phenotype:
genotype:
gametes produced:
F2 generation (cross F1 with F1)
Possible phenotypes:
Ratios:
Possible genotypes:
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green inflated pod
Ratios:
5. For the following results of a dihybrid F2 cross, determine whether of not the genes are linked.
a) 1 white short plant, 9 purple tall plants, 3 white tall plants and three purple short plants.
b) 12 purple tall, 4 white short
6. You have a purple flowered plant, but do not know whether or not it is true breeding or not. How
could you determine whether it is homozygous or heterozygous for that trait? Show all your work.
7. You are a genetics counselor at a hospital. A couple, both of whom are carriers of cystic fibrosis, a
recessive disease, want to know what the chances are that their offspring would have cystic fibrosis.
What would you tell them? Show all your work.
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8. The same couple decide to use a healthy sperm donor with the mother’s egg. What are their chances
that their offspring would have cystic fibrosis? What about being a carrier?
9. A human female carrier who is heterozygous for the recessive, sex-linked trait causing red-green
color blindness, marries a normal male. What proportion of their female children will have red-green
color blindness? What proportion of their male children will have red-green color blindness? Show all
your work.
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