Lab # _______ : Establishing Hardy-Weinberg Equilibrium
Date ________
Purpose: The purpose of this activity is to learn how Hardy-Weinberg Equilibrium is established
in populations and what assumptions and conditions are necessary to reach equilibrium.
Procedure:
1. From the gene pool, randomly select 10 cards, and then go back to your seat.
2. Count how many 'A' alleles you have and how many 'a' alleles you have. Report these
numbers for class data.
3. Record the class totals in Chart 1.
4. Calculate the frequencies of A and a in your class and record in Chart 1..
5. Now randomly pair your alleles so that you have 5 sets of alleles just like the genotypes of
diploid organisms.
6. After your teacher counts the total AA, Aa, and aa combinations in the class, record these
numbers in Chart 2 for Round 1.
7. Calculate the frequencies of each of these combinations in your class and record in Chart 2.
8. Spread your 10 cards out in one hand as if you were playing cards. Make sure that you are
the only one who can see the alleles. Go around the room and find another person to trade
with. Let that person take one of your alleles. You take one of their alleles. (Don't peek!)
Now take your new allele and put it away so that you don't trade it again.
9. Trade 4 more alleles with 4 more people (only 1 trade with each person).
10. When you have only 5 alleles left in your hand and 5 new ones that are trades, sit down!
11. Again, pair up your 10 alleles randomly so that you have 5 pairs.
12. After your teacher counts the total AA, Aa, and aa combinations in the class, record these
numbers in your Chart 2 for Round 2.
13. Calculate the frequencies of each of these combinations and record.
14. Repeat steps 8-13 two more times for rounds #3 and 4.
CHART 1: The Number and Frequency of the A and a Alleles (Class Totals)
A allele
a allele
Total
Number
Frequency
=p
=q
1.0
CHART 2: The Number and Frequency of the Different Genotypes (Class Totals)
Number
AA
Aa
Frequency
aa
Total
AA
Aa
aa
Total
Round
1
1.0
Round
2
1.0
Round
3
1.0
Round
4
1.0
Calculate ideal Hardy-Weinberg frequencies using your frequency values for 'A' (p) and 'a' (q) in
Chart 1and the Hardy-Weinberg equation: p2 + 2pq + q2 = 1 and compare them to the final
frequencies for Round 4 in the table below:
CLASS VALUES FROM ROUND 4
PREDICTED VALUES FROM HARDYWEINBERG EQUATION
Frequency of AA _______________
p2 _______________
Frequency of Aa _______________
2pq _______________
Frequency of aa _______________
q2 _______________
Questions:
1. What aspects of real populations did the following parts of the simulation represent:
A) the bag full of cards
B) the paper cards:
C) putting the paper cards in pairs:
D) exchanging cards with other people:
2. What assumptions must be met for a population in order for it to achieve Hardy-Weinberg
equilibrium?
3. How close were your final AA, Aa and aa frequencies to the ideal values?
4. How might you account for any differences between your frequencies and those predicted by
the Hardy-Weinberg equation?
5. If your population is truly in Hardy-Weinberg equilibrium, what frequencies would you
predict for AA, Aa, and aa in the next generation? Explain your answer.
6. What will happen in the next generations if the environment changes and an organism that is
homozygous for the 'a' allele has a slight disadvantage? Answer in terms of allele
frequencies.