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Sample HardyWeinberg Problems – Answers
1. In a population of 100 individuals 49% are of the NN blood type. What
percentage is expected to be MN assuming HardyWeinberg equilibrium?
A. 9%
B. 21%
C.
42%
D. 51%
E. insufficient information to answer question
Reason: q
2
= 49% or .49, so q = .7
p=.3. The genotype MN is heterozygous so the frequency = 2pq = 2(.3)(.7) = 42%
2. Attached ears is an autosomal recessive trait in humans. Assume that there are
400 people with attached ears in a population of 10000. How many individuals
would be expected to homozygous dominant?
A. 800
B. 100
C.
6400
D. 200
E. 10,000
Reason: People with attached ears are homozygous recessive (ee). Therefore, the
frequency of people with attached ears = 400/10000 = .04 = q
2
, so q = .2. Therefore, p =
.8. The frequency of homozygous dominant individuals (EE) = p
2
= (.8)
2
= .64. The total
expected number of people = .64 * 10000 = 6400 people.
3. In a population that meets the HW equilibrium assumptions, 81% of the
individuals are homozygous for a recessive gene. What percentage of the
individuals would be expected to be heterozygous for this gene in the next
generation?
Answer: 81% of people are homozygous recessive. q
2
= .81, so q = .9 and p = .1.
Therefore, the expected percentage of heterozygous individuals = 2pq = 2(.1)(.9) = .18 or
18%. Notice, this is an example where the recessive allele is more common than the
dominant allele. Remember, the terms "dominant" and "recessive" are terms that refer
only to the relationship to the alleles and whether they are expressed or not in the
heterozygote. There are many examples of genes where the recessive allele is more
common in the population.
4. Coat color in a population of rabbits is controlled by three alleles. The c+ allele
codes for brown coat, the cch allele codes for chinchilla coloration, and the ch
allele codes for himalayan coloration. The dominance relationship is c+ > cch >
ch. Suppose that in a population of 100 rabbits there were 4 himalayans and the
frequency of the chinchilla allele is .20.
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View Full DocumentWhat are the frequencies of the 3 alleles?
Answer: The 4 himalayans are homozygous recessive. Therefore, r
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 Fall '06
 11:0001:50pm
 Evolution

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