Punnett Squares Worksheet

Punnett Squares: Predicting Inheritance

Read each question carefully and answer to the best of your ability. Use Punnett squares to show your work where applicable. Remember that dominant alleles are represented by capital letters and recessive alleles by lowercase letters.

1. A   is a diagram that is used to predict the genotypes of a particular cross or breeding experiment.

2. An organism with two identical alleles for a trait is said to be  .

3. The observable physical properties of an organism are called its  .

4. The genetic makeup of an organism, including all the alleles, is its  .

5. If a homozygous dominant parent (AA) is crossed with a homozygous recessive parent (aa), what percentage of the offspring will be heterozygous (Aa)?

6. In pea plants, tall (T) is dominant over short (t). If a heterozygous tall pea plant (Tt) is crossed with another heterozygous tall pea plant (Tt), what is the expected phenotypic ratio of tall to short offspring?

7. In humans, brown eyes (B) are dominant over blue eyes (b). A brown-eyed man, whose mother had blue eyes, marries a blue-eyed woman. What are the possible genotypes and phenotypes of their children? Show your work using a Punnett square.

8. In guinea pigs, rough coat (R) is dominant over smooth coat (r). If a heterozygous rough-coated male is crossed with a smooth-coated female, what are the expected genotypic and phenotypic ratios of their offspring? Show your work using a Punnett square.

9. A Punnett square can predict the exact number of offspring with a certain genotype.

10. Incomplete dominance results in a blended phenotype in the heterozygous individual.

11. Explain the difference between genotype and phenotype. Provide an example for each using a genetic trait.

12. Describe a scenario where a Punnett square would be useful in real-world applications, beyond basic genetics problems. What information could it provide?