Punnett Squares Practice Worksheet
This worksheet provides practice problems for constructing and interpreting Punnett Squares, covering monohybrid and dihybrid crosses at a Grade 11 Biology level.
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Punnett Squares Practice
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Read each problem carefully and use Punnett Squares to determine the genotypes and phenotypes of the offspring. Show all your work.
1. In pea plants, tall (T) is dominant over short (t). Cross a heterozygous tall plant with a short plant.
a. What are the genotypes of the parents?
b. What is the genotypic ratio of the offspring?
c. What is the phenotypic ratio of the offspring?
2. In guinea pigs, rough coat (R) is dominant over smooth coat (r). If two heterozygous rough-coated guinea pigs are bred:
a. What percentage of the offspring will have a rough coat?
b. What percentage of the offspring will be homozygous recessive?
3. In cats, black fur (B) is dominant to white fur (b), and short tails (S) are dominant to long tails (s). Cross a male cat that is heterozygous for both traits (BbSs) with a female cat that is homozygous recessive for fur color and heterozygous for tail length (bbSs).
a. How many different genotypes are possible in the offspring?
b. What is the probability of an offspring having black fur and a long tail?
c. What is the phenotypic ratio of the offspring?
Determine if the following statements are true or false.
4. A Punnett square can predict the exact number of offspring with a specific genotype.
True
False
5. Incomplete dominance results in a blended phenotype in heterozygotes.
True
False
6. Explain the difference between a monohybrid cross and a dihybrid cross.
7. Describe a scenario where a test cross would be useful.
8. The observable characteristics of an organism are called its .
9. An organism with two identical alleles for a trait is said to be .
10. The different forms of a gene are called .