Download Population Genetics Lab: The Hardy

Population Genetics Lab: The Hardy-Weinberg Equation
Background: The Hardy-Weinberg Law is a mathematical model that demonstrates what happens
to allele and genotype frequencies in an ideal population.
In order to utilize this equation, several assumptions must be made:
1. No genetic mutation is occurring withing the population.
2. The breeding population is large.
3. No migration between populations occurrs.
4. All members of the population survive and reproduce. There is no natural selection.
5. Mating is random within the population.
In this lab exercise, you will examine the effects of selective predation on a small population.
The scenario: Predators (you) selectively prey upon individuals in a small population.
Prey are replaced with individuals randomly selected from an ocean to create the next generation.
The prey are fish which will be represented by beans.
White fish = white beans, express the recessive allele f
Brown fish = kidney beans, express the dominant allele, F
Procedure:
1. Empty both containers of beans into a large bowl and mix thoroughly.
2. Each group will take a smaller bowl of beans so that you may have your own population.
3. Each group will take a random population of 10 fish from the ocean.
4. In the table provided, record the number of white fish and the number of brown fish in your
random population. (Generation 1)
5. Prey upon 3 white fish from the first generation.
Note: if you do not have 3 white fish, substitute with brown fish.
6. Replace individuals who have been preyed upon, by randomly choosing 3 fish from the ocean.
Add these 3 new fish to your population. (You are replacing one fish for each one that died in
step 4).
7. Record the number of white fish and brown fish in you table, under Generation 2.
8. Prey upon 3 white fish from the second generation.
Note: if you do not have 3 white fish, substitute with brown fish.
9. Replace individuals who have been preyed upon, by randomly choosing 3 fish from the ocean.
Add these 3 new fish to your population.
10. Record the number of white fish and brown fish in you table, under Generation 3.
11. Prey upon 3 white fish from the third generation.
Note: if you do not have 3 white fish, substitute with brown fish.
12. Replace individuals who have been preyed upon, by randomly choosing 3 fish from the ocean.
Add these 3 new fish to your population.
13. Record the number of white fish and brown fish in you table, under Generation 4.
14. Prey upon 3 white fish from the fourth generation.
Note: if you do not have 3 white fish, substitute with brown fish.
15. Replace individuals who have been preyed upon, by randomly choosing 3 fish from the ocean.
Add these 3 new fish to your population.
16. Record the number of white fish and brown fish in you table, under Generation 5.
17. Calculate the allele and genotype frequencies for each generation from the data in your table.
Recall:
p2 + 2pq + q2 = 1
p+q=1
What effect does selective predation of white fish have upon allele and genotype frequencies in
subsequent generation?
Table 1: Effects of predation on allelic and genotypic frequencies
Allelic frequencies
Genotype frequencies
Generation # of individuals
2
q2
p
2pq
White
Brown
p
q
1
2
3
4
5