Post by Stern on Mar 17, 2016 13:43:36 GMT -8
BIS 2B Section B Winter Quarter, 2016
Study Questions: Population Genetics
1. Understand and be able to use the following terms:
1. population
2. gene pool
3. genotype frequency
4. allele frequency
5. evolutionary change
6. Hardy-Weinberg principle
7. Hardy-Weinberg equilibrium
8. random mating
9. nonrandom mating
10. inbreeding
11. mutation
12. beneficial versus deleterious mutations
13. gene flow
14. genetic drift
15. adaptive evolution
16. expected allele and genotype frequencies
17. observed allele and genotype frequencies
18. discrete versus quantitative traits
19. stabilizing selection
20. directional selection
21. disruptive selection
22. sexual selection
2. Distinguish between phenotypic and genotypic variation within a population.
3. When a population is in Hardy-Weinberg equilibrium, what two genetic properties of the
population remain unchanged from generation to generation?
4. List four assumptions underlying Hardy-Weinberg equilibrium in populations.
5. Several factors or forces can cause changes in allele frequencies in populations from one
generation to the next. List four of these and indicate which one leads to adaptive evolutionary
change in a population?
6. Briefly describe the process of adaptive evolution in a population including a discussion of the
phenotypic and genetic properties of a population that are required for adaptive evolution to occur.
7. The following figure illustrates three types of selection on quantitative adaptive traits in
populations. The left-most graphs show the fitness of individuals with different phenotypes of the
same trait. The right-most graphs show the distribution of the phenotypes in the population before
and after the influence of selection. Arrows indicate the direction of phenotypic change.
D:\Figures\Ch21 Evidence and Mechanisms of Evolution\highres\Life9e-Fig-21-12-0RU Natural Selection Can Operate in Several Ways.jpg
Which figure illustrates:
Directional selection: ________
Stabilizing selection: ________
Disruptive selection: ________
8. The genetic impact of migration (dispersal) on a local population depends on two properties of
the immigrants? What are these?
9. Briefly describe the process of genetic drift.
10. Why does the loss of rare alleles in a population reduce the long-term evolutionary potential of
the population?
11. Distinguish between a population bottleneck and a founder effect.
12. Does genetic drift lead to adaptive evolution? Why or why not?
Sample Problems: Population Genetics
1. A population of peppered moths has the following genotypic frequencies: aa: 0.16, Aa:
0.04, AA: 0.80. The frequency of the 'a' allele in this population is…
Is this population in Hardy-Weinberg equilibrium?
2. Our local land snail comes in two basic colors: brown-striped and black-striped. Color is
determined by alleles at a single locus, where the black allele is dominant to the brown
allele. Last week, you collected 1000 snails from your garden in Davis: 64% of these snails
were brown, and 36% were black. Based on these data, you conclude that the frequency of
the black allele in your garden population is…
a) 0.40
b) 0.60
c) 0.24
d) 0.80
e) You can’t tell from the information given.
3. If the frequency of the C allele is 0.2 in a population with only 2 alleles at this
locus, what will the frequency of heterozygotes be if the population is in Hardy-
Weinberg equilibrium?
a) 0.04
b) 0.16
c) 0.32
d) 0.64
e) 0.80
4. A moth has three alleles at a locus that controls antenna color: X1, X2 and X3. X1 is
dominant to X2 and X3; X1 produces red antennae. X2 is co-dominant to X3; X2X2 produces
yellow antennae, X3X3 produces white antennae, and X2X3 produces light yellow antennae.
The phenotypic frequencies in a population are as follows:
0.04 WHITE 0.16 LIGHT YELLOW 0.16 YELLOW 0.64 RED
Assuming that this population is in Hardy-Weinberg equilibrium, what is the frequency
of the X3 allele in this population?
a) 0.04
b) 0.20
c) 0.16
d) 0.32
e) 0.64
5. You measure the allele frequencies in the parental generation of a wolf population, and find
that f(A) is 0.6. There are only two alleles at this locus. In the next generation of wolves you
find the following genotype frequencies: f(AA) = 0.36, f(Aa) = 0.48, f(aa) = 0.16. Which
assumption of Hardy-Weinberg equilibrium is likely being violated?
a) random mating
b) large population size
c) no advantage to particular alleles
d) b and c
e) none of the assumptions is violated
6. Imagine a population of frogs with 2 color morphs (forms); green (genotypes Gg and
GG) and yellow (genotype gg). The population is initially in Hardy-Weinberg equilibrium.
Then, frogs begin to mate assortatively for color. After one generation of positive
assortative mating, you would expect to observe a change in…
a) the number of eggs laid.
b) the genotypic frequencies.
c) the population size.
d) the number of offspring produced.
e) all of the above.
7. You know that a population of elk has 2 alleles, E and e, at a single locus that controls
the color of a rump patch. The frequency of allele E, p(E) = 0.10 in the parental
generation. In the offspring of this parental generation, the genotypic frequencies are EE
= 0.01, Ee = 0.18, and ee = 0.81. You suspect that…
a) the population is in Hardy-Weinberg equilibrium.
b) elk are mating with close relatives.
c) the elk are preferentially mating with individuals with the same
color patch.
d) heterozygotes have lower relative fitness than ee genotypes.
e) ee genotypes have higher relative fitness than other genotypes.
8. One of the major eye color loci in humans has 2 alleles, b and B. The frequency of
the bb genotype is 0.36. If the population is in Hardy-Weinberg equilibrium, the
frequency of the B allele should be…
a) 0.04
b) 0.18
c) 0.40
d) 0.60
e) 0.64
9. A population of plants has 2 alleles, P and p, at a locus controlling petal color: f(P) =
0.60 and f(p) = 0.4. When you study the frequency of heterozygotes in the population
you find that f(Pp) = 0.24. This would be expected if…
a) the population is in Hardy-Weinberg equilibrium.
b) the plants self-fertilize.
c) the population has gone through a bottleneck.
d) heterozygotes are fitter than homozygotes.
e) the P allele is dominant to the p allele.
10. A population of cats has the following genotypic frequencies at a locus controlling
spotting pattern: ss: 0.36, Ss: 0.04, SS: 0.60.
(a) The frequency of the S allele in this population is
(b) Is this population in Hardy-Weinberg equilibrium?
11. Which of the following is the most appropriate level for measuring adaptive evolution?
(1) the cell;
(2) the individual;
(3) the population;
(4) the community;
(5) the ecosystem?
12. Which of the following statement is not true about allele frequencies?
a) The sum of all allele frequencies at a locus is 1.
b) If there are two alleles at a locus, and we know the frequency of one of them, we can
obtain the frequency of the other by subtraction.
c) If an allele is absent from a population, its frequency is 0.
d) If two populations have the same alleles, they will have the same allelic frequencies.
e) If there is only one allele at a locus, its frequency is 1.
Study Questions: Population Genetics
1. Understand and be able to use the following terms:
1. population
2. gene pool
3. genotype frequency
4. allele frequency
5. evolutionary change
6. Hardy-Weinberg principle
7. Hardy-Weinberg equilibrium
8. random mating
9. nonrandom mating
10. inbreeding
11. mutation
12. beneficial versus deleterious mutations
13. gene flow
14. genetic drift
15. adaptive evolution
16. expected allele and genotype frequencies
17. observed allele and genotype frequencies
18. discrete versus quantitative traits
19. stabilizing selection
20. directional selection
21. disruptive selection
22. sexual selection
2. Distinguish between phenotypic and genotypic variation within a population.
3. When a population is in Hardy-Weinberg equilibrium, what two genetic properties of the
population remain unchanged from generation to generation?
4. List four assumptions underlying Hardy-Weinberg equilibrium in populations.
5. Several factors or forces can cause changes in allele frequencies in populations from one
generation to the next. List four of these and indicate which one leads to adaptive evolutionary
change in a population?
6. Briefly describe the process of adaptive evolution in a population including a discussion of the
phenotypic and genetic properties of a population that are required for adaptive evolution to occur.
7. The following figure illustrates three types of selection on quantitative adaptive traits in
populations. The left-most graphs show the fitness of individuals with different phenotypes of the
same trait. The right-most graphs show the distribution of the phenotypes in the population before
and after the influence of selection. Arrows indicate the direction of phenotypic change.
D:\Figures\Ch21 Evidence and Mechanisms of Evolution\highres\Life9e-Fig-21-12-0RU Natural Selection Can Operate in Several Ways.jpg
Which figure illustrates:
Directional selection: ________
Stabilizing selection: ________
Disruptive selection: ________
8. The genetic impact of migration (dispersal) on a local population depends on two properties of
the immigrants? What are these?
9. Briefly describe the process of genetic drift.
10. Why does the loss of rare alleles in a population reduce the long-term evolutionary potential of
the population?
11. Distinguish between a population bottleneck and a founder effect.
12. Does genetic drift lead to adaptive evolution? Why or why not?
Sample Problems: Population Genetics
1. A population of peppered moths has the following genotypic frequencies: aa: 0.16, Aa:
0.04, AA: 0.80. The frequency of the 'a' allele in this population is…
Is this population in Hardy-Weinberg equilibrium?
2. Our local land snail comes in two basic colors: brown-striped and black-striped. Color is
determined by alleles at a single locus, where the black allele is dominant to the brown
allele. Last week, you collected 1000 snails from your garden in Davis: 64% of these snails
were brown, and 36% were black. Based on these data, you conclude that the frequency of
the black allele in your garden population is…
a) 0.40
b) 0.60
c) 0.24
d) 0.80
e) You can’t tell from the information given.
3. If the frequency of the C allele is 0.2 in a population with only 2 alleles at this
locus, what will the frequency of heterozygotes be if the population is in Hardy-
Weinberg equilibrium?
a) 0.04
b) 0.16
c) 0.32
d) 0.64
e) 0.80
4. A moth has three alleles at a locus that controls antenna color: X1, X2 and X3. X1 is
dominant to X2 and X3; X1 produces red antennae. X2 is co-dominant to X3; X2X2 produces
yellow antennae, X3X3 produces white antennae, and X2X3 produces light yellow antennae.
The phenotypic frequencies in a population are as follows:
0.04 WHITE 0.16 LIGHT YELLOW 0.16 YELLOW 0.64 RED
Assuming that this population is in Hardy-Weinberg equilibrium, what is the frequency
of the X3 allele in this population?
a) 0.04
b) 0.20
c) 0.16
d) 0.32
e) 0.64
5. You measure the allele frequencies in the parental generation of a wolf population, and find
that f(A) is 0.6. There are only two alleles at this locus. In the next generation of wolves you
find the following genotype frequencies: f(AA) = 0.36, f(Aa) = 0.48, f(aa) = 0.16. Which
assumption of Hardy-Weinberg equilibrium is likely being violated?
a) random mating
b) large population size
c) no advantage to particular alleles
d) b and c
e) none of the assumptions is violated
6. Imagine a population of frogs with 2 color morphs (forms); green (genotypes Gg and
GG) and yellow (genotype gg). The population is initially in Hardy-Weinberg equilibrium.
Then, frogs begin to mate assortatively for color. After one generation of positive
assortative mating, you would expect to observe a change in…
a) the number of eggs laid.
b) the genotypic frequencies.
c) the population size.
d) the number of offspring produced.
e) all of the above.
7. You know that a population of elk has 2 alleles, E and e, at a single locus that controls
the color of a rump patch. The frequency of allele E, p(E) = 0.10 in the parental
generation. In the offspring of this parental generation, the genotypic frequencies are EE
= 0.01, Ee = 0.18, and ee = 0.81. You suspect that…
a) the population is in Hardy-Weinberg equilibrium.
b) elk are mating with close relatives.
c) the elk are preferentially mating with individuals with the same
color patch.
d) heterozygotes have lower relative fitness than ee genotypes.
e) ee genotypes have higher relative fitness than other genotypes.
8. One of the major eye color loci in humans has 2 alleles, b and B. The frequency of
the bb genotype is 0.36. If the population is in Hardy-Weinberg equilibrium, the
frequency of the B allele should be…
a) 0.04
b) 0.18
c) 0.40
d) 0.60
e) 0.64
9. A population of plants has 2 alleles, P and p, at a locus controlling petal color: f(P) =
0.60 and f(p) = 0.4. When you study the frequency of heterozygotes in the population
you find that f(Pp) = 0.24. This would be expected if…
a) the population is in Hardy-Weinberg equilibrium.
b) the plants self-fertilize.
c) the population has gone through a bottleneck.
d) heterozygotes are fitter than homozygotes.
e) the P allele is dominant to the p allele.
10. A population of cats has the following genotypic frequencies at a locus controlling
spotting pattern: ss: 0.36, Ss: 0.04, SS: 0.60.
(a) The frequency of the S allele in this population is
(b) Is this population in Hardy-Weinberg equilibrium?
11. Which of the following is the most appropriate level for measuring adaptive evolution?
(1) the cell;
(2) the individual;
(3) the population;
(4) the community;
(5) the ecosystem?
12. Which of the following statement is not true about allele frequencies?
a) The sum of all allele frequencies at a locus is 1.
b) If there are two alleles at a locus, and we know the frequency of one of them, we can
obtain the frequency of the other by subtraction.
c) If an allele is absent from a population, its frequency is 0.
d) If two populations have the same alleles, they will have the same allelic frequencies.
e) If there is only one allele at a locus, its frequency is 1.
