Dihybrid Worksheet


Genetic Problems: Monohybrid, Dihybrid, and Test Crosses

1. In hamsters, black coat is dominant to white coat and rough coat is dominant to smooth coat. If two heterozygous black-rough coated hamsters where mated

a. What would be the phenotype ratio of the F1 generation?

b. What would be the genotype ratios of the F1 generation?

2. In garden peas, axial flower position is dominant and terminal flower position is recessive; tall vine is dominant and short vine recessive. A plant known to be purebred for tall vine and axial flowers is crossed with a plant having short vines and bearing terminal flowers.

a. What is the phenotype of the offspring?

b. What is the genotype of the offspring?

c. Predict the types of offspring (their phenotypes) that would appear in the F2 generation and their ratio.

3. In dogs, wirehair is a dominant trait, smooth hair is recessive. Two wire-haired dogs produce a male puppy that is wire-haired. To find out most quickly whether he carries the allele for smooth hair, he should be mated to what type of female?

4. In a certain animal, a breed is known that always has a hairy tail; another breed is known that always has a naked tail. How would you determine which trait is dominant?

5. In cocker spaniels, black is a dominant trait (B), red is recessive (b). Solid color is dominant (S) and white spotting is recessive (s). A red male was mated to a black-and-white female. They had five puppies as follows: 1 black, 1 red, 1 black-and-white, and 2 red-and-white. What are the genotypes of the parents?

6. Two plants having red flowers are mated. When their F1 offspring are studied, it is found that 95 have red flowers and 31 have white flowers. What is the genotype of the parents and diagram a cross to support your answer.