One of the characteristics of pea plants, Pisum sativum, which Gregor Mendel studied, was pod shape. He crossed plants that produced smooth pods with plants that produced bumpy pods.

Study Mendel’s data shown in the table below. Answer the questions that follow.

Parents / First Generations (F1) / Second Generation (F2)
Smooth pods
Bumpy pods / All smooth pods / 822 smooth pods
299 bumpy pods

1.  Which factor, smooth or bumpy pod shape, is dominant? Explain.

2.  Use the letter S or s to stand for the alleles for pod shape. Represent the dominant allele. Represent the recessive allele.

3.  Complete the table:

Phenotype / Possible Genotype
Smooth pod shape
Bumpy pod shape

4.  Make a Punnett square showing the alleles of the parent plants and the first generation offspring.

5.  Make a Punnett square showing a cross between two of the offspring shown above. Show the alleles for these parents of the second generation and their offspring.

6.  Use the Punnett square to predict the ratio of plants that produce inflated pod shape to plants that produce bumpy pod shape in the second generation of offspring.

7.  Does the ratio from above agree with Mendel’s observations?

One of the traits of pea plans that Mendel observed was seed shape. The pods were either round or wrinkled. Mendel observed that round seed shape (R) dominated over the wrinkled seed shape (r).

Complete the Punnett square to show the possible offspring of two heterozygous pea plants. Then answer the questions that follow.

R / r
R
r

1.  What two forms of the trait for seed shape did Mendel observe? ______

2.  What was the phenotype for seed shape of both parent plants? ______

3.  How many of the possible types of offspring had the same genotype as the parents? ______

4.  How many of the possible types of offspring were homozygous? ______

5.  How many of the possible types of offspring had the same phenotype as the parent? ______

6.  What was the genotype of the offspring that did not share the parents’ phenotype? ______

7.  What is the probability that two heterozygous parents would have an offspring that produced round seeds? (Show your answer as a ratio.) ______

8.  What is the function of genes?

9.  What are alleles?

10.  What is genetics?

11.  Why is Mendel known as the father of genetics?