Lab 12 Activities

Corn Coloration in an F₂ Population

Overview

In this activity, you will study the genetics of kernel color in corn. A corn cob contains hundreds of kernels. Each kernel is a seed that represents an individual organism. In the cob, we can easily see kernel color (either yellow or purple) as a phenotype.

Materials

Each lab group will need the following materials:

• 1 F₂ corn cob
• paper
• pen
• calculator

Method

1. Retrieve an F₂ corn cob from the bucket.
2. Count a total of 100 kernels.
   • Tally the number of yellow kernels within that 100 (in the dried state, anything yellow or honey colored counts as yellow).
   • Tally the number of purple kernels within that 100 (in the dried state, purple colored kernels may appear brown).
   • Ignore any speckled kernels that may have yellow and purple within them.
3. Share your counts with the other lab groups.

Analysis

Work with your lab group to answer the following questions:

1. Based on your data for the F₂ generation, which phenotype appears to be dominant? What evidence supports that claim?
2. Based on your data for the F₂ generation, which phenotype appears to be recessive? What evidence supports that claim?
3. Create a Punnett square to illustrate the expected number of each color in a simple dominant:recessive paradigm.

Kernel Coloration and Texture in an F₂ Population

Overview

In this activity, you will investigate two traits of corn: kernel color and kernel texture. You will use the same corn that was used in the previous activity.

Materials

Each lab group will need the following materials:

• 1 F₂ corn cob
• paper
• pen
• calculator

Method

1. Retrieve a dihybrid F₂ corn cob from the bucket.
2. Count a total of 200 kernels
   • Tally the number of yellow kernels that are rounded and smooth in texture.
   • Tally the number of yellow kernels that are shriveled and wrinkly in texture (honey colored).
   • Tally the number of purple kernels within that rounded and smooth in texture.
   • Tally the number of purple kernels within that  are shriveled and wrinkly in texture.
   • Ignore any speckled kernels that may have yellow and purple within them.
3. Share your counts with the other lab groups.

Analysis

Work with your lab group to answer the following questions:

1. Is there a dominant texture (rounded or wrinkled)?
2. Which is dominant, if there is?
3. Is there a color that always pairs with a texture or do these characteristics assort independently?
4. Create a Punnett square to illustrate the expected number of each color/texture combination in a simple dominant:recessive paradigm.

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