Population Genetics Lab #8 Outline
Title: Population Genetics Lab #8
Purpose
1st Paragraph: Discuss Hardy-Weinberg Law of Genetic Equilibrium. Discuss and define the
equations and the conditions that must be met for a population to remain in equilibrium. Discuss
objectives of the lab - to measure allele frequency in a population under various simulated
populations.
2nd paragraph: Discuss five sections of the lab and their objective.
 To estimate the frequency of the PTC tasting allele in a sample population by finding q.
 To simulate a population of randomly mating heterozygous individuals with an initial gene
frequency of 0.5 for the dominant allele and the recessive allele a and genotype frequencies
of 0.25 AA, 0.5 Aa, and 0.25 aa.
 To simulate selection by assuming the homozygous recessive individuals never survive and
heterozygous and homozygous survive 100% of the time.
 To simulate the heterozygous advantage.
 To simulate an island population that is small. Populations do not interact.
Briefly describe the procedure for each simulation
3rd paragraph - Relate the lab to one of the themes in AP Biology
1. Science as a Process
2. Evolution
3. Energy Transfer
4. Continuity and Change
5. Relationship of Structure to Function
6. Regulation
7. Interdependence in Nature
8. Science, Technology, and Society
4th paragraph: Briefly describe results from the lab.
Procedure:
Use a Heading for Each of the Five Test we did and describe the procedure for Each Section
Page 91: Estimating Allele Frequencies for a Specific Trait within a Sample Population
Page 92: Case 1: A Test of an Ideal Hardy-Weinberg Population
Page 94: Selection
Page 95: Heterozygous Advantage
Page 96: Genetic Drift
Data:
Table 1: Phenotypic Proportions of Tasters and Nontasters and Frequencies of the
Determining Alleles
Phenotypes
Allele Frequencies Based
on the HW Equation
Tasters
Nontasters
p
q
(p2 + 2pq)
(q2)
Class Population
#
%
#
%
North American
Population
0.55
0.45
Case 1: Hardy-Weinberg Equilibrium
Case III: Heterozygote Advantage
Initial Class Frequencies
Initial Class Frequencies
AA _____ Aa_____ aa______
AA _____ Aa_____ aa______
My Initial Genotype:_______
My Initial Genotype:_______
F1 Genotype ________
F1 Genotype ________ F6 Genotype _______
F2 Genotype _______
F2 Genotype _______ F7 Genotype _______
F3 Genotype _______
F3 Genotype _______ F8 Genotype _______
F4 Genotype ______
F4 Genotype ______ F9 Genotype________
F5 Genotype _______
F5 Genotype _______ F10 Genotype________
Final Class Frequencies:
Final Class Frequencies: (after 5 generations)
AA ______ Aa ______ aa______
AA ______ Aa ______ aa______
p _____ q ______
p _____ q ______
Final Class Frequencies: (after 10 generations)
AA ______ Aa ______ aa______
Case II: Selection
Initial Class Frequencies
p _____ q ______
Case IV Genetic Drift
Initial Class Frequencies
AA _____ Aa_____ aa______
AA _____ Aa_____ aa______
My Initial Genotype:_______
My Initial Genotype:_______
F1 Genotype ________
F1 Genotype ________
F2 Genotype _______
F2 Genotype _______
F3 Genotype _______
F3 Genotype _______
F4 Genotype ______
F4 Genotype ______
F5 Genotype _______
Final Class Frequencies:
F5 Genotype _______
Final Class Frequencies:
AA ______ Aa ______ aa______
AA ______ Aa ______ aa______
p _____ q ______
p _____ q ______
Analysis Questions
Exercise 8A: Estimating Allele Frequencies for a Specific Trait within a Sample Population
1. What is the percent of heterozygous tasters in your class (2pq)?
2. What percentage of the North American population is heterozygous for the taster
taste?
Exercise 8B: A Test of an Ideal Hardy-Weinberg Population
CASE I: A Test of an Ideal Hardy Weinberg Population
1. What does the Hardy-Weinberg equation predict for the new p and q?
2. Do the results you obtained in this simulation agree? If not, why?
3. What major assumption(s) were not strictly followed in this simulation?
CASE II: Selection
1. How do the new frequencies of p and q compare to the initial frequencies in Case I?
2. What major assumption(s) were not strictly followed in this simulation?
3. Predict what would happen to the frequencies of p and q if you simulated another
five generations.
4. In a large population would it be possible to completely eliminate a deleterious
recessive allele? Explain.
CASE III: Heterozygote Advantage
1. Explain how the changes in p and q frequencies in Case II compare with Case I and
Case III.
2. Do you think the recessive alleles will be completely eliminated in either Case II or
Case III?
3. What is the importance of heterozygotes (the heterozygote advantage) in
maintaining genetic variation in populations?
CASE IV: Genetic Drift
1. Explain how the initial genotypic frequencies of the populations compare.
2. What do your results indicate about the importance of population size as an
evolutionary force?
HARDY WEINBERG PROBLEMS
1. In Drosophilia the allele for normal length wing is dominant over the allele for
vestigal wings (vestigal wings are stubby little curls that cannot be used for flight).
In a population of 1,000 individuals, 360 show the recessive phenotype. How many
individuals would you expect to be homozygous dominant and heterozygous for this
trait?
2. The allele for unattached earlobes is dominant over the allele for attached earlobes.
In a population of 500 individuals, 25% show the recessive phenotype. How many
individuals would you expect to be homozygous dominant and heterozygous for this
trait?
3. The allele for the hair pattern called “widow’s peak” is dominant over the allele for
no “widow’s peak”. In a population of 1000 individuals, 510 show the dominant
phenotype. How many individuals would you expect each of the possible three
genotypes for this trait?
4. In the United States about 16% of the population is Rh negative. The allele for Rh
negative is recessive to the allele for Rh positive. If the student population of a high
school in the U.S. is 2,000, how many students would you expect for each of the
three possible genotypes?
5. In certain African countries 4% of the newborn babies have sickle cell anemia,
which is a recessive trait. Out of a random population of 1,000 newborn babies, how
many would you expect for each of the three possible genotypes?
6. In a certain population, the dominant phenotype of a certain trait occurs 91% of the
time. What is the frequency of the dominant allele?
Conclusion
1st Paragraph - Briefly discuss purpose - to test allele frequency in a variety of situations &
briefly restate Hardy Weinberg law of equilibrium.
2nd Paragraph - use your data and compare your initial allele frequency 0.25 AA, 0.5 AA,
and 0.25 aa with your 5th generation allele frequency for each of the five conditions. Be
specific and discuss how and why the value varies from the initial frequency. Did the results
meet your expectations? How did the various conditions affect the results?
3rd paragraph - discuss errors in the lab or ways the lab could be improved. What
extensions can be made for this lab?
4th paragraph - restate the significance of this lab to society and relate this lab to at least
one of the major themes of AP Bio.