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Hardy-Weinberg Practice Problems
Problem Set #4
1.
Given a population in Hardy-Weinberg equilibrium with allele frequencies A= 0.9 and a = 0.1, determine the frequencies of the three
genotypes, AA, Aa, aa.
Givens
Unknowns
2.
In a population that is in Hardy-Weinberg equilibrium, the frequency of the “z” allele is 0.6. What percentage of the population is
heterozygous?
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3.
In corn, yellow kernel alleles are dominant to white kernel alleles. A random sample of 1,000 kernels from a population that is in
equilibrium reveals that 910 are yellow and 90 are white. What are the frequencies of the yellow and white alleles in this
population? What is the percentage of heterozygotes in this population?
Givens
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4.
The chemical PTC tastes very bitter to most people. The inability to taste PTC is controlled by a single recessive allele. In American
Caucasians, about 70% can taste PTC. What is the frequency of the taster (T) and non-taster (t) in this population?
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5.
Coloration in the Scarlett Tiger Moth is incompletely dominant. In a population of 1612 moths, 1469 were white spotted (AA), 138
were intermediate (AA’) and 5 had little spotting (A’A’).
a.
Using this information, calculate all allele frequencies. **Start off by solving for p and q by counting actual alleles, do not solve
for p2 and q2 first**
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b.
6.
Using the information above, calculate all genotype frequencies (AA), (AA’) and (A’A’)
After graduation, you and 19 of your friends build a raft, sail to a deserted island, and started a new population, totally isolated
from the world. Two of your friends carry (are heterozygous for) the recessive CF allele, which in homozygotes causes Cystic
Fibrosis. Assuming that the frequency of this allele does not change as the population grows, what will be the instance of CF on your
island?
Givens
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For the following problems, do not assume that they are in Hardy-Weinberg equilibrium. You need to solve for each allele separately (not using
p + q = 1). Once you have solved for the allele frequencies, plug them back into the H-W equation and determine if is true or not.
7.
In a tropical forest there is a species of bird that has a variable tail length. Long is incompletely dominant over short. In one
population of 2000 birds, 614 have long tails, 973 have medium tails and 413 have short tails.
a.
What is the frequency of each allele in the population? (Hint, solve for genotype frequencies first)
Givens
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b.
8.
Is the population in Hardy-Weinberg equilibrium? (Does p + q = 1?)
A botanist is investigating a population of plants whose petal color is controlled by a single gene whose two alleles are codominant.
She finds 170 plants that are homozygous brown, 340 plants that are homozygous purple and 21 plants who petals are brownpurple. Is this population in Hardy-Weinberg equilibrium?