Name: ______
Worksheet- Easy Mendelian Genetics Problems
1. A brown mouse is mated to a white mouse and all of their offspring are brown.
a. Give a name to the gene responsible for this trait, and assign symbols for the possible alleles. Which allele is dominant?
- What are the genotypes of the mice that were crossed?
- If two of the F1brown offspring were mated together, what percentage of the F2 mice would be brown?
2. In humans, dimples are inherited as a dominant trait. A man heterozygous for dimples marries a woman without dimples.
- What are the genotypes of the couple?
Father:Mother:
- What proportion of their children will have dimples?
3. In humans the gene for farsightedness is inherited as a dominant (therefore normal vision is recessive). What fraction of children will have normal vision if a normal man marries a woman who is farsighted and had a father with normal vision?
4. In tomatoes, red fruit (R) is dominant to yellow fruit (r). A true breeding red-fruited plant is bred to a true-breeding yellow-fruited plant.
- What phenotypic ratio would you expect to see in the F1 offspring?
- If two of the F1 plants were bred, what phenotypic ratio would you expect to see in the F2 offspring?
- What genotypic ratio would you expect to see in the F2 offspring?
5. A recently married couple are both heterozygous for cystic fibrosis, a recessive genetic disorder. They would like to start a family and would like to have two children.
a. What is the probability that their first pregnancy would result in a child with cystic fibrosis?
b. What is the probability that their second pregnancy would result in a child with cystic fibrosis?
c. What is the probability that both their first and second child would have cystic fibrosis?
6. Tim & Jan both have freckles, but their son Michael does not. Use a Punnett square to show how this is possible. If Tim and Jan have another child, what is the probability that it will have freckles?
7. Both Tim & Jan (from problem 6) have a widow peak (dominant), but Michael has a straight hairline.
a. What are Tim, Jan, and Michael genotype for hairline type?
- If Tim and Jan had another child, what would be the probability of that child having both freckles and a widow peak?
8. In squash, white color is dominate over yellow. Pollen (male gametes) from a heterozygous white fruited plant is placed on the pistil (female organ) of a yellow fruited plant. Determine the genotypes of the parents and the genotypes and phenotypes of the F1 generation.
9. The gene for brown hair is dominant over that for blond hair. If two heterozygotes married, what proportions of these two traits would you expect in their children?
10. In guinea pigs, the allele for black fur (B) is dominant over the allele for white fur (b). A black male guinea pig is mated to a white female guinea pig. The offspring were 7 black and 6 white guinea pigs. What are the genotypes of the parents?
Father: Mother: