Download Lab 10: Population Genetics

Week 10 Lab
POPULATION GENETICS SIMULATION EXPERIMENTS
NOVEMBER 15-19, 2004
1
Thought Questions:

The Hardy-Weinberg may seem over-simplistic or unrealistic. What are the pros and cons of
a simple vs. a complex model? A realistic vs. an unrealistic model?

If you know the genotype frequency in a population, can you predict the allele frequency?
Do you need to make any assumptions to make this prediction?

If you know the allele frequency in a population, can you predict the genotype frequency?
Do you need to make any assumptions to make such a prediction?

Sometimes conditions for Hardy-Weinberg equilibrium are disrupted temporarily:

What trends in allele frequencies or genotype frequencies would indicate that such a
disruption is happening?

During such a disruption, what might happen to the relationship between allele and
genotype frequencies?

Once all of the conditions for Hardy-Weinberg equilibrium are restored, what will
happen to allele frequencies? To genotype frequencies (and how fast)?

In general, why might continuous traits be more difficult to study than Mendelian traits?
Why might they be easier?

When conservation biologists or wildlife managers are studying population genetics, what
types of traits are they likely to examine, continuous traits or Mendelian traits? What types
of Mendelian traits might they use? Is this a sensible choice?
Learning Objectives:
(1) Review the Hardy-Weinberg theorem and the conditions that must be met for the theorem
to predict allele frequencies and genotype frequencies.
(2) Demonstrate important factors that influence population genetics in a simulated population
of moths.
(3) Simulate the effects of changing conditions such as
 genetic drift, and
 modes of natural selection

directional selection

stabilizing selection

disruptive selection
Readings: Read Ch. 23 in Cambell et al. Review Ch. 14 if you are not completely comfortable with
basic principles of genetics such as probability, alleles, or mutation.
Lab 10-18
LAB OVERVIEW
The Big Picture:
Evolution occurs in populations of organisms, rather than in individual organisms, and it typically takes a
long time, from decades to millions of years. It is difficult to study speciation or other major evolutionary
changes in an introductory biology class. Such changes have been observed both in the laboratory and in
the field, and several examples will be described in the recitation lecture. In lab, we will use the important
technique of simulation modeling to study evolutionary change.
BEFORE LAB
TAKE-HOME QUIZ DUE AT THE BEGINNING OF LAB THIS WEEK:
Attending recitation and reading the lab and your text should help you to
complete this week’s take-home quiz that is due at the very beginning of lab this
week. Do the take-home quiz individually; do not work in groups!
FIRST HOUR
IN GROUPS
Work on the simulation models using the lab computers. Do Part One ‘Testing
the Hardy-Weinberg Theorem’ and Part Two: ‘Genetic Drift’ in their entirety. If
you finish, review and discuss Part Three: ‘Modes of Natural Selection.’
SECOND HOUR
IN GROUPS
Work on Part Three: ‘Modes of Natural Selection’ and plan an oral presentation
with members of your group to present your approaches to the exercise and the
results of your simulated experiment.
THIRD HOUR
IN GROUPS
Each group will have 10 minutes to present results from Part Three: ‘Modes of
Natural Selection.’
 For Part One (Testing the Hardy-Weinberg Theorem) summarize the
results using the worksheets provided and written interpretation of your
results. The lab manual includes bold-faced questions that you should
address in your interpretations.
 For Part Two (Genetic Drift), use a combination of the worksheets
provided and a written summary of your results and their interpretation.
Again, pay attention to the questions in bold-faced type.
TAKE HOME
ASSIGNMENT
IN GROUPS
 For Part Three (Modes of Natural Selection)

Your group will be assigned a specific “goal” – (Group 1)
directional selection for black moths, (Group 2) directional
selection for white moths, (Group 3) stabilizing selection, or
(Group 4) disruptive selection. Be sure to put your group number
and your assigned “goal” on the worksheet provided.

Listen carefully to and take notes of the results of each group’s
natural selection study. Everyone will be required to turn in a
written assignment that covers all of the various modes of natural
selection. This information may also be on your recitation final
exam.
due at beginning
of week 12 lab,
11/29-12/3
The worksheets and accompanying written interpretations (and answers to
bold-faced questions) should be signed by you and your group partners to
indicate that each of you has contributed equally.
Lab 10-19
Introduction
Genetic changes that occur in generations of populations over long periods of time are the basis for
evolution of a species. In a population of any species, there are typically individuals that show differences
in phenotype for a particular trait. These differences may represent genetic variation in the population.
For example, the peppered moths (Biston betularia) occur in two different colors or morphs. One morph
has light, almost white-colored wings with small flecks of brown, while the other morph is predominantly
black or very dark brown in color. This trait is controlled by a single gene and is an example of a discrete
or Mendelian trait.
Another example of variation both among species and within populations is found in the genus of
Galapagos finches, (Neospiza), studied by Darwin during the voyage of the Beagle and more recently by
Peter and Rosemary Grant of Princeton. Galapagos finches show variation in beak size. This is a complex
trait controlled by many genes. It is an example of a continuous or quantitative trait.
The underlying basis for inherited phenotypic differences is the genetic composition of an organism. Each
organism has many genes, with each gene occurring at a locus, a physical location along a chromosome.
The specific genetic material at a given locus is called an allele. The specific allele(s) occurring at one
locus or at many loci is called the genotype of an individual organism. (In diploid organisms, there are two
copies of each chromosome and so two alleles for each locus.)
The expression of the genotype is the phenotype. Among the many different organisms within a
population, there may be just one type of allele occurring at a given locus, or there may be two or more
alleles at that locus. The term gene pool refers to the population’s total range of allelic variation at one or
more loci. Mutations, both random and induced, are the sources of new alleles that cause the inherited
variation that is essential for evolution of populations and species.
Quantifying genetic variation in populations
Geneticists interested in population genetics study allele frequencies as a way to predict whether a
population is evolving. When there are two or more alleles for a particular gene, it is sometimes possible to
determine the relative proportion of each allele in a gene pool.
If one is studying two alleles called A and a for a particular gene at a known locus, p can be designated as
the frequency of the A allele, and q as the frequency of the a allele. The sum of p and q represents 100% of
the alleles for this gene in the population. In mathematical notation:
p+q=1
Consider a population of 100 individuals, each of which has two alleles for this gene. Therefore, if 80
percent of the alleles are A, then p = 0.8. Twenty percent of the alleles would then be a; therefore q = 1 – p
= 0.2. Also notice that p = 1 – q.
What is the relationship between the allele frequency and the genotype frequency in a population? In
1908, two geneticists, G. H. Hardy and W. Weinberg, independently proposed an equation to relate allele
frequency to genotype frequency. The equation recognizes that if the organisms are diploid, then they may
carry three possible combinations of these alleles: AA, Aa, or aa.
Lab 10-18
For each genotype, the frequency can be determined by remembering how alleles segregate from the two
haploid parental gametes (each carrying just one allele) to make the new, diploid zygote that grows into an
offspring (with each diploid cell carrying two alleles).
The probability of inheriting the A allele from any one parent is 0.8, the frequency of that allele in the
overall population. The probability of inheriting the A allele from the other parent is also 0.8. These two
probabilities multiply together (see Campbell et al. 6th edition pp. 254-255 for a review of probability).
So, the probability of a genotype being AA is p  p = p2 = (0.8)2 = 0.64. Similarly, the probability of the
offspring’s diploid genotype being aa is q2 = (0.2)2 = 0.04.
Finally, the probability of the offspring’s diploid genotype being Aa, with an A allele from one parent and
an a allele from the other parent is 2pq = 2(0.8)(0.2) = 0.16. Multiplication by 2 is necessary because there
are ‘two ways’ to have the Aa genotype (i.e., Aa, or inheriting A from one parent and a from the other
parent; and aA, inheriting a from one parent and A from the other parent.)
The genotype frequencies of the three possible combinations of these alleles must add up to 100% and they
do: p2 + q2 + 2pq = 0.64 + 0.04 + 2(0.16) = 1.00. We would predict 64 AA, 4 aa and 32 Aa genotypes in
this population of 100 individuals.
This overall view of the population also makes sense if you recall that the frequency of all alleles was:
p + q = 1.0
And so the sum of all genotype frequencies can be determined from the following equation:
(p + q)2 = (p + q)(p + q) = p2 + 2pq + q2 = 1.0
Finally, it is important to point out that there may not be any variation within a population for a given
allele. If all individuals in a population are homozygous for an allele being studied, that allele is known as
a fixed allele. It is also possible for more than two alleles to exist for a given gene, a more complex
situation that we will not address in today’s lab.
Applications of the Hardy-Weinberg theorem.
Rather than simply review the Hardy-Weinberg theorem, let’s think about a population geneticist who has
the job of monitoring a population.
First, her boss is asking her for the allele frequency in a population, but she only has information about the
genotype frequency. Can she predict the allele frequency? Yes, at least for the current generation. She
can simply count up how many alleles there are in a population.
But, what if she needs to predict either the allele frequency or the genotype frequency in the next
generation? This is trickier. To determine whether or not allele and genotype frequencies are changing
from one generation to the next, she needs information about natural selection, genetic drift, mating
patterns, migration,and mutation.
Lab 10-19
What if she is in the reverse situation: her boss wants to know genotype frequency in the current
generation of a population, but she only has information about allele frequency. She doesn’t really need to
worry about natural selection, because that only happens between one generation and the next. But it is
actually not possible to make this prediction without making certain assumptions about the mating pattern
in the population, migration, mutation, and the occurrence of genetic drift.
OK, what does the Hardy-Weinberg theorem have to do with this? The Hardy-Weinberg theorem states
that allele frequencies and genotype frequencies will remain constant over several generations provided a
number of conditions are met.
These conditions are as follows:
1. Large breeding population. The effect of random changes in allele frequencies (genetic drift) is
greatly reduced in a population with large number of individuals.
2. Random mating. Individuals in a population show no preference for mating with other individuals
of a particular phenotype.
3. The alleles under study do not mutate. Alleles are not being mutated to create new alleles, which
would change the gene pool and alter genotype frequencies in a population.
4. There is no migration of individuals into or out of the population. Therefore, the gene pool will not
change due to migration.
5. There is no selective advantage for any individual. If all individuals in a population have an equal
chance of surviving and reproducing, then all of the genotypes represented in the population are
equally viable and all alleles should be inherited equally.
These five conditions are required if a population is to maintain Hardy-Weinberg equilibrium. If all
conditions are met in a population, then no change in allele or genotype frequency will occur in that
population. Also, when these conditions are met, there is a one-to-one relationship between allele
frequency and genotype frequency, such that genotype frequency can be predicted from allele frequency.
Such a model may seem overly simplistic and rather unrealistic, since few (if any) populations in nature
meet all of these conditions. As you become more familiar with modeling in ecology and evolution, you
may realize that models are actually quite helpful when they fail to match what happens in the real world
and the data collected from the real world.
When the conditions for Hardy-Weinberg break down, it is an indication that there may be because changes
in the gene pool occurring in a population — a process known as microevolution. It is important to
understand how deviations from Hardy-Weinberg criteria can reflect microevolution. Such deviations will
be further described in the assignments that accompany this lab as you design experiments that will help
you learn how different mechanisms of microevolution can influence population genetics.
Lab 10-18
An example of an evolving population
A famous example of natural selection involves British moths called peppered moths (Biston betularia).
These moths are found in two different colors or morphs. One morph has light, almost white-colored wings
with small flecks of brown, while the other morph is predominantly black or very dark brown in color. This
trait is controlled by a single gene, and you may recall that we used it as an example of a discrete or
Mendelian trait.
Because birds are predators of peppered moths, wing color is an important camouflage for moths — natural
selection can occur for wing color and for the alleles affecting wing color. White morphs can blend well
into the light, peppered appearance of lichen-colored trees but black or brown moths cannot. Black or
brown morphs can blend well into the dark bark of trees affected by pollution, but white moths cannot.
Presumably, natural selection was occurring both before and after industrialization. But the details of that
natural selection depend on the selective environment — in this case, whether lichen-covered tree bark is
common or whether industrial pollution kills off the lichens and darkens the bark on most trees.
Modeling exercises
You will use PopGenLab to learn how changes in important parameters of population genetics can
influence evolution in simulated populations of moths. These moths resemble peppered moths, but are not
exactly the same as them. You are provided with moths living in tree stands. A single gene with two
alleles controls wing color of these moths, and each genotype produces a different color pattern.
Moth survival depends on the insect’s ability to blend against the bark of the trees. Three different tree
types have bark colors that match the colors of the moths in the simulation. The experiments that you set
up and analyze in PopGenLab will provide you with an important understanding of the factors influencing
Hardy-Weinberg equilibrium and natural selection.
By varying parameters such as allele frequencies and survival rates of each genotype, population numbers,
population carrying capacity, mating patterns, and the frequency of population crashes due to natural
disasters, you will design experiments to help you understand how each parameter can affect evolution
within the population of moths.
Getting to Know PopGenLab
This assignment is designed to help you become familiar with the operation of PopGenLab by applying the
Hardy-Weinberg theorem to learn about Hardy-Weinberg equilibrium parameters. The first screen that
appears in PopGenLab shows you an input parameter page with a table listing the default parameters for
the laboratory conditions that you can manipulate when setting up your experiments. You should enlarge
this window before you begin working.
Before you can set up any experiment in PopGenLab, you must be familiar with the input parameters that
you can manipulate for this population of moths. A brief description of each input parameter is provided
below. Refer back to this section as needed when you are working on different assignments.
Click on the Change Inputs button to see all the parameters you can manipulate for this lab. A new page
will open with buttons for each of the input parameters located at the left side of each page (genotype
frequency will be open as the first input parameter). Click on each input parameter and read the
Lab 10-19
descriptions below. Change each parameter so that you can become familiar with how each input
parameter operates. You can set these to exact values by clicking on the scoll bars.
Genotype Frequency - allele frequency for wing color (controlled by a single gene) is shown for
two alleles, A and a, as a pie chart of the phenotype resulting from each of the three possible
genotypes: AA (black moths), Aa (brown moths), and aa (white moths). Notice that the default
frequency is 50% for each allele.
Tree Types - three different types of trees are available. These trees provide habitat and food for
the moths. Each tree has a different color of bark, which corresponds to the color of each of the
three moths. Moth survival from birds as natural predators depends on a moth's ability to blend
against tree bark with a color similar to the moth's wings. Notice that the default value provides an
equal proportion of each tree type.
Number of Stands - the number of groups (stands) of trees determines the number of moth
populations. The default value is one tree stand (one moth population).
Stand Size - the number of trees in an individual stand. Stand size directly influences the number
of moths that can live within the stand. The maximum number of moths that the stand can support
over time is called the carrying capacity of the stand. The default value is set to accommodate a
large population, 4000 moths. This is the largest carrying capacity available in the simulation.
You can adjust stand size and carrying capacity to much smaller values.
Migration Rate - controls the rate of migration and mixing of populations between different tree
stands. Note: The Migration Rate button is shaded and inactive as the default because you must
select at least two different populations (tree stands) for this input parameter to be active.
Mating Pattern - the type of mating can be selected as either assortative (individuals select partners
with phenotypes similar to their own), random, or disassortative (individuals select partners with
different phenotypes). The default is random mating. You can alter the degree of assortative or
disassortative mating.
Disaster Frequency - controls the frequency of tornadoes, hurricanes, and the weather effects that
typically accompany these natural disasters. Any population of organisms can be influenced by
environmental disasters such as drought, flooding, hurricanes, tornadoes, and disease. In
PopGenLab, the default value is for a benign environment with no disasters (Never). This
frequency can be changed to produce occasional disasters (Sometimes) or frequent disasters
(Often).
After you have finished this introduction to the input parameters, click the Reset button at the left of the
screen to return all input parameters to their default values.
Lab 10-18
Part One: Testing the Hardy-Weinberg Theorem
Now that you are familiar with the basic parameters in PopGenLab, set up the following experiment to help
you understand Hardy-Weinberg equilibrium and the factors that influence a state of equilibrium in a
population.
Leave all input parameters at their default values. Check the genotype frequency value and note the allele
frequency values for comparison after you have run the experiment. You now have an experimental
population with equal allele frequencies; genotype frequencies of 50% brown, 25% white, 25% black;
equal proportions of each of the three tree types; one tree stand with a carrying capacity of 4000 (this is a
large population of moths); random mating; and because the disaster frequency is set at “Never,” the
population size of these moths will remain constant.
Based on these conditions, does each moth genotype have an equal chance of survival or is
there a selective pressure (positive or negative) on one or more genotypes? Write your
answer and a brief explanation below:
Return to the initial page of the simulation if you are still in the Change Inputs view. Find the pop-up
menu, showing the number of generations, in the lower left corner of the screen. Leave generation number
set at its default value of 100. Click the Run Experiment button to run this simulation.
When the experiment has finished running, a separate page will appear that presents the results of your
experiment. Note: The program will automatically show you the genotype frequencies for the first
generation. This may make it look like nothing has happened in your simulated experiment. To see what
happened over several generations, you need to use the scroll bar to move from generation one through the
various generations up to generation 100.
Note: Any of the following data views can be saved to disk or printed by clicking the Export button.
Clicking on this button will open a separate window with your plot or table. From this window you
can then save your data to your hard drive or a disk, and you can print your data by using the print
feature of your browser software.
For your lab assignment, you need to complete worksheet one.
The following data can be examined:
Genotype Frequency – to see what happened to genotype frequency after the initial generation one,
you need to click and drag the slider to show genotype frequency as the frequency of AA (black),
Aa (brown), and aa (white) genotypes. Data is represented as a pie chart showing the percentage
of each different colored moth in the total population for each generation. Y ou can drag the bar
from left to right and back again to scroll through the 100 generations. The worksheet provides
space to record genotype frequency in generation 50 and generation 100.
Lab 10-19
Allele Frequency - click on the check boxes to show a plotted view of allele frequency for either
allele (A or a) or for both alleles together. Data is represented as the percentage of an allele in each
generation. The worksheet provides space to record allele frequency in generation 50 and
generation 100.
Heterozygosity - the percentage of heterozygous moths in each generation over time.
Population Size - the number of moths in each generation over time.
Allele Distribution - plots the frequency of the A allele vs. the number of populations in each
generation over time. Here you are looking at just one population, so this is not a very meaningful
view.
Textual Data - text columns of raw data for allele frequencies.
Input Summary - a summary table of the initial input parameters for the experiment.
Repeat this experiment at least three times to determine if the results from this experiment are consistent.
Use the provided worksheet to record the outcome of the repeated simulations.
1.
Look at the allele and genotype frequencies from this first simulation. Is there a change
in allele frequency over time? Is there a change in genotype frequency over time? What
did you observe? Explain your answers.
2.
How do the actual genotype frequencies for this first simulation compare to the HardyWeinberg predictions?
You should do at least two additional sets of experiments, using different sets of initial genotype
frequencies. Before you run either experiment, use the Hardy-Weinberg equation to make a prediction
about what will happen to this population. There are spaces for you to record your predictions.

First, change the genotype frequencies from the 0.25 AA, 0.50 Aa, 0.25 aa condition, but in such a
manner that you keep the allele frequencies at 0.50 A and 0.50 a. There is a second table on the
worksheet to record your conditions and results from this set of experiments. Run a few trials
before you decide to record your data in the table.

Second, change the genotype frequency in a way that will also change the allele frequency.
(Notice that the allele frequency is always printed in the upper right hand corner of the window as
you manipulate the genotype frequencies). There is a third table on the worksheets to record your
conditions and results from this set of experiments. Again, run a few trials before you decide to
record your data in the table.

3. Third, with these two follow-up simulations to test the H-W equation, what did you
discover? Did the results agree with the predictions? Why or why not?
Lab 10-18
Part Two: Genetic Drift in One Population
Random changes in the genotypes of a population are known as genetic drift. Genetic drift has the
potential to change the genetic composition of populations. Carrying capacity of an environment can
influence how a population changes in response to genetic drift because carrying capacity is an important
factor that determines the size of a population. Large populations rarely show strong effects of genetic
drift, but genetic drift in a small population can have a great influence on allele and genotype frequencies in
that population. With a change to smaller population sizes, there may also be a change in heterozygosity.
The following exercise is designed to help you understand important aspects of genetic drift as a potential
cause of microevolution.
Formulate a hypothesis to predict the effect of a decrease in tree stand carrying capacity on
allele and genotype frequencies. Write your hypothesis below:
For Part One of the lab, you have already set up an experiment and run it with default values for all of the
Hardy-Weinberg conditions. To return to the default parameters, remember that you can click “Reset” in
the “Change Inputs” window.
Now you need to run a series of experiments with default parameters for all conditions except tree stand
size. For each experiment, reduce tree stand size by 25%. (For example, run an experiment at the default
value of 4000, then change tree stand size to 1000, then to 250, and so forth.)
After each experiment, make notes of what you observed for allele and genotype frequencies in the
appropriate worksheet. Be sure to repeat each experiment several times, and think about the results as you
transfer the data from the output pages in the software to your worksheets.
After you have completed this series of experiments and the worksheets, answer the following questions.
4.
What happened to allele and genotype frequencies in this experiment? How do these
results compare with what you observed for allele and genotype frequencies under the
default conditions? In answering this question, be sure to include the hypothesis that you
wrote down above, and state whether your hypothesis was supported (or not).
5. What happened to the percentage of heterozygotes? Explain these results.
Lab 10-19
Part Three: Modes of Natural Selection
Different modes of natural selection can select for or against a particular trait, thus affecting the balance of
phenotypes in the population. For example, in a mode of natural selection called directional selection,
selection favors individuals with one of the extreme phenotypes — a phenotype at either the top end or the
bottom end of the range of phenotypes. For example, all black or all white moths can be considered
extremes while brown moths represent an intermediate phenotype. In stabilizing selection, extreme
phenotypes are selected against and intermediate phenotypes have higher rates of reproduction or survival.
In contrast, diversifying selection favors individuals with extreme phenotypes at either end of a range over
individuals with an intermediate phenotype.
In the following experiment you will investigate how fitness — the probability that a particular phenotype
will survive and produce offspring (which is a measure of survival and reproduction of different genotypes)
— affects changes in allele frequency in the population.
Begin an experiment with default conditions for Hardy-Weinberg equilibrium for all parameters except the
number of tree stands and genotype frequencies. Set the number of stands to 100. Change the distribution
of tree types to set up the experiment assigned to your group:
Group One: directional selection for dark color,
Group Two: directional selection for light color,
Group Three: balancing selection,
Group Four: diversifying selection.
For each experiment, look at different genotype and allele frequencies. Try experiments with the different
conditions of selection, such as very weak selection. Or, try initial allele or genotype frequencies where the
selected genotype is very rare (close to zero).
There is a worksheet for recording the results of your simulations of natural selection. If you need
additional copies of this worksheet, they will be available during lab.
Depending on the conditions you are trying, you may want to look at different generations other than 50 or
100. For example, if selection acts very quickly, you may want to include generation 2, 3, 4, or 5 on your
worksheet. Or, if selection acts very slowly, you may want to increase the number of generations (there is
a pull-down window for doing this in PopGenLab) and record a generation much later than generation 100
on the worksheet.
Lab 10-18
Your group will need to present your experiments and the results and interpretations to the rest of the class
during lab today. Those presentations should make it possible for all students to address the following
questions:
6. What happens to allele frequency in the case of directional selection?
7. Does directional selection for dark color produce the same result as directional selection for
light color?
8. What happens to allele frequency in the case of stabilizing selection?
9. What happens to allele frequency in the case of disruptive selection?
10. Are small differences in fitness effective in changing allele frequencies?
11. Under what mode of selection might genetic variation be maintained? Explain.
Lab 10-19
Assignments
Due at the beginning of Week Lab 12, November 29-December 3, 2004
What to turn in at the beginning of lab the week after the Thanksgiving holiday:
Part I – one per group
Worksheet 1: Testing Hardy-Weinberg Equilibrium
Typed answers to Questions 1-3
Part II – one per group
Worksheet 2: Genetic Drift
Typed answers to Questions 4-5
Part III – one per group
Worksheet 3: Modes of Natural Selection (may be multiple pages)
Typed answers to Questions 6-11
Tips for success:

Be sure to put the names of all of your group’s members on all of the worksheets.

You should have time during lab to complete the PopGenLab exercises and to discuss your
answers to their associated questions.

It is wise to complete the majority of your assignment during class, when you can interact not only
with your group members but also with your instructor. You and your group members may want
to meet outside of class or use e-mail to work on the final versions of your answers to the required
questions. It is certainly possible but not necessary for your group to meet outside of class to use
PopGenLab on-line to do additional simulations.

All group members should include their signatures on a cover sheet accompanying what you turn
in, consistent with the policies for group work specified in the introduction to your lab manual.
Your signatures indicate that all group members have contributed equally to the assignment.
Lab 10-18
Group members __________________________________________________________________________________
Biology 2003
Time/day/instructor ___________________________
LAB 10, WORKSHEET 1: TESTING THE HARDY-WEINBERG THEOREM
Fall 2004
Population size (carrying capacity) = _____
Disaster frequency = _____
Number of tree stands (number of populations) = _____
Mating pattern = _______
Proportion of tree types: 1/3 white; 1/3 brown; 1/3 black
Simulation One
Allele
frequency:
Genotype
frequency
Simulation Two
Simulation Three
Initial
After 50
After 100
After 50
After 100
After 50
After 100
Conditions
generations
generations
generations
generations
generations
generations
A
0.50
a
0.50
AA
0.25
Aa
0.50
aa
0.25
Lab 10-18
LAB 10, WORKSHEET 1: TESTING THE HARDY-WEINBERG THEOREM
Initial conditions
Predictions
Simulation One
50 generations
100 generations
Simulation Two
50 generations
100 generations
Allele frequency:
A
0.50
a
0.50
Genotype frequency
AA
Aa
aa
Initial conditions
Predictions
Simulation One
50 generations
100 generations
Allele frequency:
A
a
Genotype frequency
AA
Aa
aa
Lab 10-19
Simulation Two
50 generations
100 generations
LAB 10, WORKSHEET 2: GENETIC DRIFT
Disaster frequency = ________
Initial
Conditions
4000
Stand size:
Number of tree stands = ________
Mating pattern = ________
Simulation One
After 50
After 100
generations
generations
Simulation Two
After 50
After 100
generations
generations
Simulation Three
After 50
After 100
generations
generations
Simulation One
After 50
After 100
generations
generations
Simulation Two
After 50
After 100
generations
generations
Simulation Three
After 50
After 100
generations
generations
Allele frequency:
A
0.50
a
0.50
Genotype frequency:
AA
0.25
Aa
0.50
aa
0.25
Heterozygosity:
Initial
Conditions
1000
Stand size:
Allele frequency:
A
0.50
a
0.50
Genotype frequency:
AA
0.25
Aa
0.50
aa
0.25
Heterozygosity:
Lab 10-18
LAB 10, WORKSHEET 2: GENETIC DRIFT
Initial Conditions
Stand size:
Simulation One
After 50
After 100
generations
generations
Simulation Two
After 50
After 100
generations
generations
Simulation Three
After 50
After 100
generations
generations
250
Allele frequency:
A
0.50
a
0.50
Genotype frequency:
AA
0.25
Aa
0.50
aa
0.25
Heterozygosity:
Initial
Conditions
60
Stand size:
Simulation One
After 50
After 100
generations
generations
Simulation Two
After 50
After 100
generations
generations
Allele frequency:
A 0.50
a 0.50
Genotype frequency:
AA 0.25
Aa 0.50
aa 0.25
Heterozygosity:
Lab 10-19
Simulation Three
After 50
After 100
generations
generations
LAB 10, WORKSHEET 3: MODES OF NATURAL SELECTION
Multiple copies of this worksheet are available.
Your group may run as many simulations with as many different initial settings as you like.
Number of tree stands = 100
Disaster frequency = ________
Mating pattern = ________
Stand size = 4000
Mode of
selection:
Stabilizing
Disruptive
Directional for ___________
You may wish to record data from one or two individual stands
AVERAGE
Stand number:
(of all 100 stands)
Stand number:
Initial
After 50
After 100
After ?___
After 50
After 100
After ?___
After 50
After 100
After ?___
Conditions
generations
generations
generations
generations
generations
generations
generations
generations
generations
Survival probability:
white
for simplicity, assume survival probabilities remain constant
brown
black
Allele frequency:
A
a
Genotype frequency:
AA
Aa
aa
Lab 10-18
LAB 10, WORKSHEET 3: MODES OF NATURAL SELECTION
Multiple copies of this worksheet are available.
Your group may run as many simulations with as many different initial settings as you like.
Number of tree stands = 100
Disaster frequency = ________
Mating pattern = ________
Stand size = 4000
Mode of
selection:
Stabilizing
Disruptive
Directional for ___________
You may wish to record data from one or two individual stands
AVERAGE
Stand number:
(of all 100 stands)
Stand number:
Initial
After 50
After 100
After ?___
After 50
After 100
After ?___
After 50
After 100
After ?___
Conditions
generations
generations
generations
generations
generations
generations
generations
generations
generations
Survival probability:
white
for simplicity, assume survival probabilities remain constant
brown
black
Allele frequency:
A
a
Genotype frequency:
AA
Aa
aa
Lab 10-19