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Hardy-Weinberg Practice Problems
p2 + 2pq + q2 = 1
p+q=1
1. 1 in 1700 US Caucasian newborns have cystic fibrosis. C for normal is dominant over c for
cystic fibrosis.
a. When counting the phenotypes in a population why is cc the most significant?
b. What percent of the above population have cystic fibrosis (cc or q 2)?
c. From the above numbers you should be able to calculate the expectant frequencies of all the
following (assuming a Hardy-Weinberg equilibrium):
Allele Frequency Calculations:
a. Which allele would you calculate first? __________ Why?
b. c= q= ?
c. Which equation do you now need to use in order to find p?
d. Find p: C=p=?
Genotype Frequency Calculations:
a. CC- Normal homozygous dominant = p2 = ?
b. cc- Diseased homozygous recessive = ?
c. Cc- Heterozygous (carrier)= ?
f. It has been found that a carrier is better able to survive diseases with severe diarrhea. What
would happen to the frequency of the "c" if there was a epidemic of cholera or other type of
diarrhea producing disease?
Would "c" Increase? Decrease?
2. If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what
percentage of the population will be more resistant to malaria because they are
heterozygous(Ss) for the sickle-cell gene?
Allele Frequency Calculations:
Genotype Frequency Calculations:
3. In a population that is in Hardy-Weinberg equilibrium, 16 % of the individuals show the
recessive trait. What is the frequency of the dominant allele in the population?
Allele Frequency Calculations:
4. On a hillside there are 100 flowering plants. One gene pair controls flower height. Tall (T 1) is
incompletely dominant over short (T2). There are 81 tall plants, 18 medium plants, and 1 short
plant. What is the frequency of each allele in the population?
Allele Frequency Calculations:
5. Same hillside, same plants, but next spring there are 500 plants and we are going to look at
flower color. Flower color blue (B) is completely dominant over flower color white (b). There
are 490 blue plants and 10 white plants. What is the frequency of each allele in the population?
Allele Frequency Calculations:
6. In a flock of 342 scarlet ibis, 102 individuals have dominant, green colored legs. Find the
frequencies for the dominant and recessive alleles and genotype frequencies.
Allele Frequency Calculations:
Genotype Frequency Calculations:
7. Phenylketonuria is a severe form of mental retardation due to a rare autosomal recessive
allele. About one in 10,000 newborns are affected with this disease. Calculate the frequency of
the carriers.
Allele Frequency Calculations:
Genotype Frequency Calculations