Name __________________________ Period _____
Basic Genetics Practice Problems
Part 1: Mendel’s Works
Mendel made the following crosses with pea plants. Complete the Punnett Squares and answer the following questions.
1.
He crossed a red flowered R plant with a white flowered r plant. His results were 126 red flowered plants and
122 white flowered plants. Which of the Punnett squares above best show the parents and offspring that could
give these results?
2.
He crossed a red flowered plant with a white flowered plant. His results were 307 red flowered plants and 0
white flowered plants. Which of the Punnett squares above best show the parents and offspring that could give
these results?
3.
He crossed a red flowered plant with a red flowered plant. His results were 306 red flowered plants and 110
white flowered plants. Which of the Punnett squares above best show the parents and offspring that could give
these results?
4.
He crossed a red flowered plant with a red flowered plant. His results were 300 red flowered plants and 0 white
flowered plants. Which of the Punnett squares above best show the parents and offspring that could give these
results?
Part 2: Monohybrid Crosses
1.
In minks, coat color is controlled by a single gene. The allele for a brown (B) coat is dominant to the allele for
silverblue (b) coats.
a. A homozygous brown mink was crossed with a silverblue mink. There were 9 offspring in the F1
generation. What color were they?
b.
Two of the offspring from the F1 generation above were mated. What would the ratio of brown to
silverblue offspring be in the F2 generation?
i. What fraction of the F2 generation will be homozygous brown?
ii. Heterozyous?
iii. Homozygous silverblue?
2.
In domestic cats, the gene for Tabby stripes (T) is dominant over the gene for no stripes (t).
a. If a breeder crossed a heterozygous Tabby cat with a stripeless cat, what percent of the F1 generation
would have tabby stripes?
b.
There is a recent demand in pet stores for Tabby cats. As a breeder, which two cats from the F1
generation above would you cross to produce the most Tabby kittens? Why?
3.
If you had a Tabby cat and wanted to know if this cat was Homozygous or Heterozygous, what type of cat could
you breed your Tabby with to prove its genotype? Explain your answer.
4.
In squash, the allele for white fruits is dominant over the allele for yellow fruits. If a white-fruited plant is
crossed with a yellow-fruited plant and all of the offspring are yellow, what are the possible genotypes of the P
generation and F1 generation?
5.
In humans, normal skin pigmentation is due to a dominant gene, albinism to its recessive allele.
a. A normal man marries an albino woman. Their first child is an albino. What are the genotypes of these
three persons?
b.
If they have more children, what would they probably be like, and in what ratio?