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Post-Section Genetics of Selection & Hardy-Weinberg Equilibrium
Worksheet (20 pts)
5 points are for section participation, 15 are for the answers on this worksheet.
Type answers to the following questions directly into this file using a different colored font
and save it as Genetics of Selection_YourNETID.pdf. Upload the completed worksheet as a
pdf by 9:00PM Sunday.
Section participation score: __ / 5
Question 1. Cystic fibrosis is a genetically determined disease that causes an overproduction of
fluid and mucus in the lungs and sweat glands. Cystic fibrosis occurs at a surprisingly high
frequency in certain human populations; one in 25 people of European descent is a carrier of the
CF allele. Scientists have often wondered if CF persists in these populations because those with
one copy of the CF allele may have higher resistance to diseases that cause fluid to leave the
body such as cholera.
Use the Radford simulator that you used in section. To access the online simulator go to:
http://www.radford.edu/~rsheehy/Gen_flash/popgen/
Question 1. You will run two simulations using the following relative fitness values
collected from two different locations (N=1000). Here A1 is the normal gene and A2 is the
CF gene.
Location 1
Location 2
A1A1
0.4
1.0
A1A2
1.0
0.9
A2A2
0.4
0.8
When initially sampled, allele frequencies at the two localities are as follows:
f(A1) = 0.99, f(A2) = 0.01
a) Set the population p value (initial frequency of A1 allele) at 0.99, number of generations
at 100, set population size equal to 1000, and number of populations to 1. Set Fitness
values at: A1A1 = 0.4, A1A2 = 1.0, and A2A2 = 0.4. Select Go. Observe how f(A2), and
the genotype frequencies change over time in Population 1 and answer the following.
b) Paste a screenshot of the Change in A1 and A2 Allele Frequencies Over Time and
the Genotype Frequencies graph below. [btw – if you hover your mouse over the graph
a camera icon will appear at the top allowing you the option of downloading a png of the
graph.]
Paste the Change in A1 and A2 Allele Frequencies Over Time and the Genotype
Frequencies graph here:
(i) The most advantageous genotype at ‘Location 1’ is:_____ (1 pt) (Total: 6 pts)
(ii) Describe what is happening in this population to the three genotypes and the two
alleles: (1 pt) (Total: 7 pts)
(iii) What predictions can you make about allele loss or fixation if the scenario continues
for another 100 generations? (1 pt) (Total: 8 pts)
c) Set the initial frequency of A1 allele at 0.01, number of generations at 100, set population
size equal at 1000, and number of populations at 1. Set Fitness values at: A1A1 = 1.0,
A1A2 = 0.9, and A2A2 = 0.8. Select Go. Observe how the frequency of the A2 allele, and
the genotypic frequencies change over time in Population 2 and answer the following.
d) Paste a screenshot of the Change in A1 and A2 Allele Frequencies Over Time and
the Genotype Frequencies graph below. [btw – if you hover your mouse over the graph
a camera icon will appear at the top allowing you the option of downloading a png of the
graph.]
Paste the Change in A1 and A2 Allele Frequencies Over Time and the Genotype
Frequencies graph here:
(i) The most advantageous genotype at ‘Location 2’ is:_________ (1 pt) (Total: 9 pts)
(ii) In this location A1 is: (circle one) (1 pt) (Total: 10 pts)
Additive
Dominant
Recessive
(iii) What happens to the frequency of A1A2 and A1A1 over time? Why? (1 pt) (Total: 11
pts)
(iv) What predictions can you make about allele and genotype loss or fixation if the
scenario continues for another 100 generations? (1 pt) (Total: 12 pts)
[more questions below!]
Question 2. In some populations of gray squirrels, a mutation will
occasionally produce jet black (A2A2) or brown-black (A1A2)
squirrels. You sample 85 individuals in from a population in Kent,
Ohio and observe the following:
Phenotype
Gray
Brown-Black
Jet Black
Genotype
A1A1
A1A2
A2A2
Counts
55
12
18
a) Is this population in Kent, Ohio in HWE? Perform the
necessary calculations and show all of your work (you will not receive credit for the
correct answer if you do not give the formula you used to calculate it). Write one
sentence stating whether the population is in HWE. Round to the hundredths. If the sum is
> 3.84, the observed numbers of genotypes are different from those expected based on HardyWeinberg proportions. (4 pts) (Total: 16 pts)
You sample 85 individuals from another locality near Battle Creek, Michigan and the counts are
as follows:
Phenotype
Gray
Brown-Black
Jet Black
Genotype
A1A1
A1A2
A2A2
Counts
11
48
26
b) Is the population close to Hardy-Weinberg equilibrium? Perform the necessary
calculations and show all of your work (you will not receive credit for the correct answer
if you do not give the formula you used to calculate it). Write one sentence stating
whether the population is in HWE. Round to the hundredths. If the sum is > 3.84, the
observed numbers of genotypes are different from those expected based on Hardy-Weinberg
proportions. (4 pts) (Total: 20 pts)