The Hardy-Weinberg equation POGIL activity helps model genetic variation using

(allele frequencies) and

(genotype frequencies). It establishes a baseline for non-evolving populations where
is the dominant allele frequency (
),
is recessive (
),
is homozygous dominant (
),
is heterozygous (
), and
is homozygous recessive (
)

newtopiccyclegrowin
7 pages
Genetics
newtopiccyclegrowin
7 pages
Genetics
248
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The Hardy-Weinberg Equation 1
The Hardy-Weinberg Equation
How can we make predictions about the characteristics of a population?
Why?
Punnett squares provide an easy way to predict the possible genotypes for an offspring, but it is not practi-
cal to perform a Punnett square analysis on all possible combinations of all members of a population to
predict what the population might look like in the future. For that we must turn to statistics. The Hardy-
Weinberg equation is a tool biologists use to make predictions about a population and to show whether or
not evolution is occurring in that population.
Model 1 – Controlled (Selective) Mating
Bb
Bb
Bb
bb
bb
bb
Bb
Bb
Bb
bb
bb
bb
Males Females
Bb
Bb
Bb
bb
bb
bb
Males Females
Bb
Bb
Bb
bb
bb
bb
1. How many mating pairs are illustrated in Model 1?
2. Describe the parents in each mating pair in Model 1. Use terms such as homozygous, heterozy-
gous, dominant, and recessive.
3. Use two Punnett squares to determine the possible genotypes for offspring from the pairs.
2 POGIL
™
Activities for AP* Biology
4. If each mating pair has one offspring, predict how many of the first generation offspring will
have the following genotypes.
BB Bb bb
5. Imagine the 24 beetles in Model 1 as a population in an aquarium tank.
a. How likely is the pairing scenario in Model 1 to take place during the natural course of things
within that tank?
b. Why is Model 1 labeled “Selective Mating”?
6. List two other pairings that might occur in the population in Model 1 if the beetles were allowed
to mate naturally.
7. If the population of beetles in Model 1 mated naturally would your prediction for the offspring
in Question 4 still be valid? Explain.
8. Discuss in your group the limitations of Punnett square predictions when it comes to large popu-
lations. Summarize the key points of your discussion here.
The Hardy-Weinberg Equation 3
Model 2 – Population Genetics
Bb bb
Bb Bb
BbBb
Bb bb
bb bb
bb bb
Bb bb
Bb Bb
BbBb
Bb bb
bb bb
bb bb
Males Females
9. Compare the organisms in the population in Model 1 with the organisms in the population in
Model 2.
10. Individually match up twelve mating pairs from the population in Model 2 that might occur in a
natural, random mating situation.
11. Compare your set of mating pairs with other members of your group. Did your mating scheme
match anyone else’s in the group?
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