Evaluation of a Population (F2 Generation)

Activity B

Introduction

In this activity you will plant a population of Wisconsin Fast Plants2 to simulate a real population. The plants that you will be using are the F2 offspring from a cross between a purple stemmed, yellow-green leaf plant and a non-purple stemmed, normal leaf plant. After allowing the plants to grow for a week, they will be scored. The allele frequencies of this generation will be compared to the allele frequencies of the original generation.

Procedure :

Planting

1. Put approximately 55 g of soil into the large container.

2. Add 50 mL of water and mix thoroughly until all the soil is evenly moistened.

3. Push the wick through the center of the precut x in the bottom of the smaller container.

4. Pour approximately 25 g of the moistened soil into the smaller container.

5. Distribute 16 fertilizer pellets on top.

6. Spread about 50 g more of moistened soil on top of the fertilizer pellets.

7. Evenly space 10 Fast Plants seeds on the surface of the soil.

8. Add another 25 g of moistened soil evenly over the Fast Plants seeds.

9. Water gently with approximately two pipets full of water.

10. Rinse the large container and then fill the container half full with water.

11. Place the smaller container on top of the larger container so that the wick of the smaller container is in the water and the smaller container is being supported by the larger container.

12. Place these in the lighted space designated by your teacher.

Scoring

1. After a week, examine your plants for the two stem colors, purple and non-purple (green).

2. Count the number of plants showing each characteristic and record the data on Table 4 (Tab 3).

3. Collect the class data and record it on Table 4 (if using the 8-station kit).

Data Analysis

1. Use the class data to calculate the frequency of each allele. Record it on the data sheet.

2. Use the class data to calculate the frequency of each genotype. Record it on the data sheet (Tab 4).

3. Use the class data to calculate the number of each genotype. Record it on the data sheet (Tab 4).

4. Answer the Laboratory Questions for Activity B (Tab 5).

Lab Questions:

1. Given that the parental generation had allele frequencies of ANL (p) at 0.50 and anl (q) at 0.50, use your experimental allele frequencies to explain whether this population is evolving or not with respect to these alleles.

2. Imagine that a population of herbivorous animals who dislike the taste of anthocyanin is introduced into the environment of the Fast Plants. How would this affect the allele frequencies in the Fast Plants population? Over time, what do you think would happen?

3. Explain what you would expect to see in allele frequencies if a population were evolving

4. Consider your activity with Fast Plants. Explain why natural selection acts on phenotypes rather than on genotypes.

5. Imagine that you are a member of a committee assigned to evaluate a report of neurofibromatosis, a disorder inherited through a dominant allele. Neurofibromatosis is a condition in which noncancerous tumors grow along nerves. The report concludes that because three-quarters of the offspring of parents who are heterozygous for eurofibromatosis will have the disorder, eventually, 75% of the population will have neurofibromatosis. Do you agree or disagree with the report's conclusion? Explain your reasoning.