1. In pea plants, tall (T) plants are dominant over short (t) plants. Make Punnett Squares for each of the following crosses and give phenotypic ratios of offspring.
Example: a. TT x tt
T
t[Tt]
Phenotypic ratio: 1 (There is only one possible phenotype in the offspring)
Note: I removed the borders from the top and left sides of the Punnett Square by selecting them and setting the border width to zero.
b. Tt x tt
c. Tt x Tt
2. In pea plants, purple flowers (P) are dominant over white (p) flowers.
a. Use a Punnett Square to determine the phenotypic ratio of offspring for this cross: A heterozygous purple plant crossed with a homozygous purple plant.
b. A cross between two pea plants produces offspring in which approximately 50% of the flowers are white and 50% are purple. What are the genotypes of the parents? Show punnett square to support your answer.
c. A cross between two purple pea plants yields approximately 25% of the offspring exhibiting white flowers.What are the genotypes of the parents? Show punnett square to support your answer.
3. A person who is homozygous for dimples has children with a person who is homozygous for "no dimples". All of the kids have dimples. Which allele is dominant and which is recessive? Explain your answer.
4. In guinea pigs, black fur is dominant. If a black guinea pig is crossed with a white guinea pig and the litter contains a white offspring, what is the genotype of the black-haired parent? Defend your answer.
5. In minks, brown is dominant over silver-blue color.
a. What color of offspring would you predict if you crossed a homozygous brown mink with a silver-blue mink?
b. What would the genotypic and phenotypic ratios in the offspring of two F2 generation mink from the question above be if they were crossed? Show a Punnett square to support your answer.
6. In dragons, the ability to breath fire is a recessive trait. Homozygous dominant dragons cannot produce fire or smoke at all. Heterozygous dragons can produce smoke, but no fire.
a. Cross a fire breathing dragon with a homozygous dominant dragon. What would be the phenotypic ratio of the offspring?
b. Cross two smoke-producing only dragons. Are any of the offspring able to produce fire? Show punnett square to support your answer.