WLHS / AP Bio / Monson
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PROBLEM SET: Population Genetics / Hardy-Weinberg Theorem
1) If the frequency of a recessive allele is 30% in a population of 200 people, how many people would you predict
would show the dominant phenotype? How many people would be carriers (heterozygotes) of this allele? How
many people would show the recessive phenotype?
2) From a sample of 278 American Indians, the following MN blood types were obtained: MM = 78, MN = 139, NN
= 61. Calculate the gene frequency of M and N.
3) Among 86 Indians from Central America, the frequencies of M and N were 0.74 and 0.26 respectively. Calculate
the expected percentages of individuals with M, MN and N type blood.
4) In a population in Hardy-Weinberg equilibrium, if the genotype frequencies are 81% AA, 18% Aa, and 1% aa,
what are the frequencies of the A and a alleles, respectively?
5) Tay-Sachs disease is inherited as a Mendelian recessive and occurs in Ashkenazic Jews at a frequency of 1 per
3,600 births. Estimate the percentage of this population that are heterozygotes (carriers) of the Tay-Sachs allele.
6) In a population in Hardy-Weinberg equilibrium, there are two alleles, A and a, for a particular gene. If the
frequency of the a allele is 0.4, what is the frequency of the genotype AA? of the genotype Aa? of the genotype aa?
7) In a population at Hardy-Weinberg equilibrium, what proportion of individuals are homozygous dominant,
heterozygous, and homozygous recessive if the frequency of the recessive allele, a, is 0.01?
8) Phenylketonuria is a disease in which the affected individuals lack an enzyme required for the metabolism of the
amino acid phenylalanine. It is inherited as a Mendelian recessive and appears at the rate of one in every 15,000
births in the U.S. What percentage of this population is homozygous NORMAL at the locus where the PKU allele
occurs? What percentage of the population is heterozygous for this trait?
9) A recent study has shown that 9.0% of the natives on the south pacific island of Pago Fuago possess an allergic
reaction to coconuts. This reaction, which appears to be an immune response similar to hives, is thought to be due
to the action of a recessive gene (h). The population of this tropical paradise is 5000. Complete the following chart
based on this information.
The frequency of the
The total number of
(H) gene =
homozygous nonallergic Pago
Fuagens =
The frequency of the
(h) gene =
The total number of Pago
Fuagans that are carriers of the
(g) allele and phenotypically
normal =
The total number of (h)
genes on Pago Fuago
=
The total number of Pago
Fuagens that suffer from this
allergic condition =
10) In Drosophila, the allele for normal length wings is dominant over the allele for vestigial wings (vestigial wings
are stubby little curls that cannot be used for flight). In a population of 1,000 individuals, 360 show the recessive
phenotype. How many individuals would you expect to be homozygous dominant and heterozygous for this trait?
11) The allele for the ability to roll one’s tongue is dominant over the allele for the lack of this ability. In a population
of 500 individuals, 25% show the recessive phenotype. How many individuals would you expect to be homozygous
dominant and heterozygous for this trait?
12) The allele for the hair pattern called “widow’s peak” is dominant over the allele for no “widow’s peak.” In a
population of 1,000 individuals, 510 show the dominant phenotype. How many individuals would you expect of
each of the possible three genotypes for this trait?
13) In the United States, about 16% of the population is Rh negative. The allele for Rh negative is recessive to the
allele for Rh positive. If the student population of a high school in the U.S. is 2,000, how many students would you
expect for each of the three possible genotypes?
14) In certain African countries, 4% of the newborn babies have sickle-cell anemia, which is a recessive trait. In
such a population, out of a random population of 1,000 newborn babies, how many would you expect for each of
the three possible genotypes?
15) In a certain population, the dominant phenotype of a certain trait occurs 91% of the time. What is the frequency
of the dominant allele? What is the frequency of the recessive allele? If this population consists of 215 individuals,
how many individuals would be heterozygous for this trait?