Download Hardy Weinberg Equilibrium Activity

Hardy Weinberg Equilibrium Activity
Materials:
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3 or more decks of playing cards depending on the size of class
a calculator to determine frequencies during activity
blackboard to record data that all can see
Description of Activity:
Platypapyrus foursuitii (playing card critter) is a diploid organism. Each card represents alleles in the gene pool, and two
cards together represents the genotype of an individual. A student can hold any number of different individual genotypes
depending on the sample size you want. (The more individuals, the closer to expected values.) For a class of 25, you can
have a population size of 50 by giving each student four cards. You will, therefore, need 100 cards.
For purposes of illustration, assume a population size of 50 individuals, each individual comprised of two cards. A one-locus,
two allele model is simulated by red and black cards. All red cards, regardless of suit, represent the R allele. The black cards
represent the B allele. Three possible genotypes result from this: RR, RB and BB. Since the focus is on what the genes do, it
is better to ignore the concept of phenotype.
The actual running of the activity is as follows:
1. Eliminating the jokers, sort the cards from 3 decks into a red pile and a black pile.
2. Create 20 individuals homozygous for the B allele by making 20 pairs of black cards.
3. Create 30 individuals homozygous for the R allele by making 30 pairs of red cards.
4. The individual cards make up the gene pool of Platypapyrus foursuitii – 40 black cards and 60 red cards. The frequency
of the black allele is 40/100 = 0.4, and the frequency of the red allele is 60/100 = 0.6. Because of the way the population is
set up, all of the individuals are homozygous, either BB or RR. The frequencies of diploid genotypes are 0.6 for RR (30/50),
0.4 for BB (20/50) and 0 for RB (0/50). Work through these frequencies with the students.
5. Distribute all the pairs of cards to the students, reminding them to keep the pairs intact until they receive further
instructions.
6. The first round of random mating can now take place. In order to ensure “random mating”, it is important that potential
mates keep the colour of their cards hidden. Mating is reciprocal – each time two organisms mate they trade one card. The
students get up and mill about the room, keeping their cards in pairs. To ensure adequate mixing of the population, have
the students say “hello” when they encounter another student. The fourth time they say “hello” to someone they can trade
cards. This means giving one card of a pair to the other person and receiving a card from the other person in return. When
a card of a pair has been replaced by mating, that pair should not be mated again in this round of mating, so mated pairs of
cards should be stored away. Students mill around until all of their individuals have been mated.
7. Have the students return to their desks and together they can calculate the frequencies of genes and genotypes again.
Since no cards have either entered of left the gene pool, the frequency of R will still be 0.6, and the frequency of B will 0.4.
However, the frequency of genotypes will have changed. Determine the number of RR, RB and BB. Since there is a total of
50 individuals, the frequency of each genotype is easily determined by counting the number of each type and dividing by
50. The exact numbers will vary somewhat each time you do it but will hover around RR = 0.36, RB = 0.48 and BB = 0.16.
Teacher Instructions:
Round One:
 Count prior to the round (should have 8 homozygous blacks and 22 homozygous reds) (HW
Equilibrium)
o Calculate the p and q (p=0.73 and q=0.27)
2
2
o Calculate the p , 2pq, and q
 Count after the round (should have some heterozygous individuals as well)
o Calculate the p and q (should be the same)
2
2
o Calculate the p , 2pq, and q
Round Two:
 Repeat again and count after the round is over (HW Equilibrium)
o Calculate the p and q (should be the same)
2
2
o Calculate the p , 2pq, and q
Round Three:
 Prior to the round, kill off all 3, 5, 7, and 9 Red Card Carriers and run the round (VIRUS – Natural
Selection)
o Calculate the p and q (should be different)
2
2
o Calculate the p , 2pq, and q
Round Four:
 Prior to the round, individuals that were killed off are given new cards (all black) (MIRGRATION –
Gene Flow)
 Run the round and count
o Calculate the p and q (should be different)
2
2
o Calculate the p , 2pq, and q
Round Five:
 Must mate with the first person you say hello to not the fourth (Mate Selection)
 Last five people to mate die and cards do not count
o Calculate the p and q (should be different)
2
2
o Calculate the p , 2pq, and q
Round Six:
 Prior to the round, the individuals killed off are given new cards (red coated cards) (Mutations)
 Run the round and count
o Calculate the p and q (now a new variation r)
Round Seven:
 Prior to the round, anyone who has a new card gets two more to play with (act like two
separate individuals)
 Run and count
o Calculate the p and q (now a new variation r)
Round Eight:
 Prior to the round, kill off 4 rows (BOTTLENECK – Genetic Drift)
 Run and count
o Calculate the p and q (now a new variation r)
Observations:
Round
1.
2.
3.
4.
5.
6.
7.
8.
P
q
r
N/A
N/A
N/A
N/A
N/A
2
P
2pq
Q
2