### 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.