Name ________________________________________________Block ______ Date ___________
Honors Genetic Problems (30 Points)
Solve the following problems in the space provided. All work must be done in pencil to receive credit.
Make sure to make a key to identify each allele, show the cross, complete a Punnett Square and
calculate the genotypic and phenotypic ratios for each problem. You will not get full credit unless
you show ALL your work.
1. The tall trait is dominant over the short trait in plants. Green coloring is dominant over yellow
coloring for plants. Show a Punnett square that illustrates a cross between two individuals that are
both heterozygous for both color and height.
Key:
Genotype:
Cross: ____________ x _____________
Phenotype:
2. Japanese four o’clock plants display incomplete dominance. The gene for red plants is
incompletely dominant over the gene for white plants. What ratio may be expected in a cross
between a red-flowered Japanese four o’clock plant and a white one?
Key:
Cross: ________ x ________
Genotype:
Phenotype:
3. In cattle, codominance exists between the gene for a red coat and the gene for a white coat
resulting in offspring with a roan coat. Determine the possible genotypes and phenotypes of an
offspring produced from a cross of two roan individuals.
Key:
Cross: ________ x ________
Genotype:
Phenotype:
4. What are the possible genotypes and phenotypes of a woman has O blood and a man who has
type AB blood.
Key:
Cross: ________ x ________
Genotype:
Phenotype:
5. Adrenoleukodystrophy (ALD) is a recessive sex linked disorder that causes the build up of fat in
the brain. It is carried on the X chromosome. Cross a father who does not have ALD with a mother
who is a carrier for ALD.
Key:
Cross: ____________ x _____________
Genotype:
Phenotype:
6. In humans, red-green colorblindness is a recessive trait and is carried on the X chromosome. A
man who is color blind marries a woman who is a carrier of the trait; determine the possible
genotypes and phenotypes off their offspring.
Key:
Cross: ____________ x _____________
Genotype:
Phenotype: