Activity 1: The Friar Who Grew Peas

1. Discuss the information found in the Background Agricultural Connections section of the lesson. You may want to use the Peas in a Pod Powerpoint Slides or excerpts from the book Gregor Mendel: The Friar Who Grew Peas by Cheryl Barbadoe.
2. Make a Punnett square model on the board to illustrate the results of Mendel’s experiments with pea plants. Yellow pompoms represent the dominant gene for yellow seeds and green pompoms represent the recessive gene for green seeds. Use two yellow pompom magnets for Parent 1 and two green pompom magnets for Parent 2. In this case, we are crossing two parents with purebred traits. When a purebred pea plant with yellow seeds is crossed with a purebred pea plant with green seeds, there is a 100% probability that the offspring will have yellow seeds. If this F1 generation (the first filial generation resulting from a cross between the first set of parents) is crossed, the results will be different.
3. Discuss the meaning of the Punnett square with the students. Write the following on the board to explain how dominant and recessive genes are expressed: When two dominant genes are present, the dominant gene will be expressed. When a dominant and a recessive gene are present, the dominant gene will be expressed. When two recessive genes are present, the recessive gene will be expressed.
4. Make another Punnett square model on the board to illustrate the F2 generation (the second filial generation resulting from a cross between two individuals from the F1 generation). Use one yellow and one green pompom magnet for Parent 1 and one yellow and one green pompom magnet for Parent 2. In the F2 generation, we are crossing two parents with hybrid traits. When a hybrid pea plant with yellow seeds is crossed with another hybrid pea plant with yellow seeds, there is a 75% probability that the offspring will have yellow seeds and a 25% probability that the offspring will have green seeds. It is important to note that in the case of a hybrid, the dominant trait is what will be expressed.

Activity 2: Pompom Punnett Squares

1. Fill lunch-size paper bags with 12 yellow and 12 green pompoms. Divide students into groups of four. Provide each student with a Punnett Square activity sheet and each group with a Punnett Square Chart and a bag of yellow and green pompoms.
2. In each group, students will take turns being Parent 1 and Parent 2. Each parent will close their eyes and choose two pompoms from the bag. They will then begin creating a Punnett square on their chart by placing their pompoms in the space provided for Parent 1 and for Parent 2. The group will use the remaining pompoms to fill out the rest of the Punnett square.
3. Each student will record the results on their Punnett Square activity sheet using a Y to represent yellow seeds and a g to represent green seeds. Underneath each Punnett square, students can record the probability of the offspring having yellow or green seeds.
4. This process can be repeated as many times as desired by choosing new pompoms from the bag. Pompoms can be replaced with other props to represent different pea plant traits, such as tall and short pipe cleaners for stem height. Use the Pea Plant Traits Chart to determine whether the traits are dominant or recessive when creating Punnett squares for different traits.