bio 352 exam 2

1. Hardy-Weinberg equilibrium (HWE) provides a quantitative basis for studying genetics in natural

populations. Which of the following is NOT a necessary assumption for HWE?

a. Similar genotypes mate preferentially with one another.

b. Populations are assumed to be very large.

c. There is no migration into or out of the population.

d. There is no mutation at the locus of interest.

e. The gene is assumed to not be under natural selection.

a. Similar genotypes mate preferentially with one another.

2. Speciation can occur when different populations accumulate enough genetic differences that they

become unable to reproduce with one another. The evolutionary force called ________________ is

thought to greatly retard this process.

a. gene flow

b. genetic drift

c. inbreeding

d. natural selection

e. mutation

a. gene flow

3. A single copy of a new allele appears in a population of orchids when pollen is transferred from a

distant population. The allele is neutral with respect to selection. There is a 1% probability of this

allele becoming fixed through the action of genetic drift. How many orchids are in the population?

(Assume that the size of the population is constant, and that this species of orchid is diploid.)

a. 10

b. 20

c. 50

d. 100

e. 500

c. 50

Probability of fixation = the frequency in the population. 1% = 1/(2N) so N = 50

4. A salamander larva may or may not metamorphose into an adult at age 2 months. This decision is

based on levels of hormones in the body. If the hormone levels are higher than a certain value,

metamorphosis will always occur. If they are less than this value, metamorphosis almost never

occurs. "Do I metamorphose after 2 months ?" is best characterized as a

a. continuous trait

b. meristic trait

c. threshold trait

d. Mendelian trait

e. determinant trait

c. threshold trait

5. Genetic variation can be studied in natural populations using

a. DNA sequence differences

b. differences in the electrophoretic mobility of proteins

c. morphological characters only if they have a genetic basis

d. A and B only

e. A, B and C

e. A, B and C

a. DNA sequence differences

b. differences in the electrophoretic mobility of proteins

c. morphological characters only if they have a genetic basis

6. Expected heterozygosity is

a. the number of heterozygotes seen in a sample from a natural population.

b. the number of heterozygotes you expect to see in an inbred population.

c. the probability that an allele is randomly chosen once from a gene pool.

d. the probability that the same allele is randomly chosen twice from a gene pool.

e. the probability that two different alleles are randomly chosen from a gene pool.

e. the probability that two different alleles are randomly chosen from a gene pool.

Data:

"1" ATCCACGTCGTCATCACTG... 32

"2" ATCCATGTCGTCATCACTG... 6

"3" ATCCACGTCGTCATCACTA... 1

"4" ATCCACGTCGTCATCACTT... 1

7. What is the frequency of allele 1 in the mitochondrial gene pool?

a. 0.032

b. 0.32

c. 0.64

d. 0.80

e. 32

d. 0.80

32/40

8. Imagine a simple natural selection model with random mating and only viability selection. All heterozygous Aa offspring survive to adulthood, but all homozygous individuals die. If we take a very large sample from this population and test for Hardy Weinberg genotypic proportions, what will we find?

a. Neither adults nor newborn offspring are in HW proportions.

b. Both adults and newborn offspring are in HW proportions.

c. Adults are in HW proportions but not newborn offspring.

d. Newborn offspring are in HW proportions but not adults.

e. If you sample this population and determine everyone's genotype, you will not be able to test for

HW proportions.

d. Newborn offspring are in HW proportions but not adults.

-See the lectures on natural selection models. This is exactly what happens in the models. HW

proportions are always found in zygotes if there is random mating.

9. During a wildfire, a large population of butterflies in an isolated canyon in Tierrasanta goes extinct.

One month later, a large storm event blows 10 butterflies in from a population to the north that is fixed for A. During the same storm, 10 butterflies blow in from a different population to the south that is fixed for a.

The 20 butterflies mate randomly in this canyon, and the population grow quickly to a very large size (10,000 butterflies). There is random mating in the canyon every generation. There is no more dispersal.

After the 20 founders arrive, how long until we expect the canyon to reach genotype frequencies p2,

2pq and q2?

a. 0 generations after colonization (the 20 colonists will be in HW equilibrium when they all arrive)

b. 1 generation after colonization

c. 20 generations after colonization

d. 10,000 generations after colonization

e. never

b. 1 generation after colonization

-One generation of random mating is required for HW proportions

10. In population genetics, fitness is calculated using

a. the number of offspring that survive and reproduce

b. the physical strength of the organism

c. the number of times an organism mates in its lifetime

d. the overall health of the organism

e. a jar of M and M's, some dice and a slot machine.

a. the number of offspring that survive and reproduce

11. If you are outbreeding, then you choose your mates

a. without considering whether they are related to you.

b. if they are related to you.

c. if they are very closely related to you.

d. if they are unrelated to you.

e. if the look like you

d. if they are unrelated to you.

13. A population of swallows is studied. Adult birds are scored at a single locus that has two alleles. Of

120 randomly surveyed birds, 85 are BB, 12 are Bb and 23 bb. Does this locus depart from HardyWeinberg

frequencies? (For 1 degree of freedom χ2 > 3.84 is significant.)

a. Yes. χ2 = 1534.4

b. Yes. χ2 = 101.6

c. Yes. χ2 = 63.5

d. No. χ2 = 1.8

e. No. χ2 = 0.5

c. Yes. χ2 = 63.5

14. Which microevolutionary forces could be responsible the data in question 13?

a. inbreeding

b. natural selection

c. mutation

d. A or B only

e. A, B or C

d. A or B only

Inbreeding creates a deficiency of heterozygotes.

Mutation operates too slowly to generate a huge deficiency of heterozygotes in one generation.

15. There is a population of wildflowers in a field that is infinitely large. In this field, all flowers produce the same number of offspring. There is a 10% chance of self-pollinating and a 90% chance of mating randomly with any flower. Assume there is no mutation, migration or natural selection.

Over time, what will happen to genetic variation at a locus that is polymorphic right now?

a. Ho will decrease to zero, and He will decrease to zero.

b. Ho will decrease to zero, and He will increase to one.

c. Ho will decrease to zero, and He will reach a stable equilibrium between zero and one.

d. Ho will reach a stable equilibrium between zero and one, and He will reach the same stable

equilibrium.

e. Ho will reach a stable equilibrium between zero and one, and He will reach a different stable

equilibrium between zero and one.

e. Ho will reach a stable equilibrium between zero and one, and He will reach a different stable

equilibrium between zero and one.

17. Purple plumage in parrots is a caused by a homozygous recessive condition at a single locus. The

forward rate of mutation from the "green gene" to purple is 0.01. The backward rate of mutation is

so small that it can be ignored. The frequency of the purple allele is 0.10. What will frequency of

the purple allele be in one generation?

a. 0.110

b. 0.109

c. 0.100

d. 0.901

e. 0.999

b. 0.109

-Frequency of green after on generation is 0.9*(1 - 0.01) = 0.891

So frequency of purple = 1-0.891 = 0.109

18. In a population of petunias, there are only one-third as many heterozygotes as you would expect

from random mating. The average petunia has an inbreeding coefficient of _______.

a. 0.167

b. 0.300

c. 0.333

d. 0.340

e. 0.667

e. 0.667

=1-(1/3)

21. Which of the following is true about mutation?

a. Mutation is a powerful microevolutionary force that can change allele frequencies dramatically

in a short time.

b. Under some models of mutation, heterozygosity decreases to zero unless it is balanced by

another force (like natural selection).

c. Mutation rates are usually around 1% - 10% per gene per generation.

d. The one way mutation model leads to random increases or decreases in gene frequencies from

generation to generation.

e. In the two-way mutation model, the mutation rates µ and ν decline over time to zero.

b. Under some models of mutation, heterozygosity decreases to zero unless it is balanced by

another force (like natural selection).

c is wrong by many orders of magnitude. d is wrong because the one way mutation model does not

produce random fluctuations: the population moves steadily towards fixation for a.

22. Which of the following is NOT true about the "island model" of migration?

a. There is no mainland in this model, only islands.

b. The island model assumes that migration rates are constant over time, and equal in all

populations.

c. The island model ignores any natural selection on the locus being studied.

d. The island model generally takes longer to reach equilibrium than a mutation model would.

e. The island model shows that allele frequencies p and q will eventually be the same everywhere,

unless there is another force acting (like drift).

d. The island model generally takes longer to reach equilibrium than a mutation model would.

23. What is the link between Darwin's theory of evolution and the population genetic models of natural

selection?

a. Darwin believed that mutations drive adaptation over short time periods, which is shown in the

models.

b. Darwin thought that fitness should increase over time. The models show this mathematically.

c. Darwin believed that heritable traits do not evolve, which is shown in the natural selection

models.

d. Darwin believed in "survival of the fittest", which means mathematically that the selective

coefficient s increases as fitness w increases.

e. Darwin believed that the least fit individuals will contribute the most to the next generation.

This is how the natural selection models are constructed.

b. Darwin thought that fitness should increase over time. The models show this mathematically.

-Average w for the population increases over time.

24. Which model of natural selection maintains polymorphism in most situations?

a. complete dominance

b. partial dominance

c. overdominance

d. underdominance

e. all of the above

c. overdominance

25. One percent of San Diego residents have excessive nose hair, caused by a recessive condition at a

single locus. Assuming that there is random mating in San Diego, how many people are

heterozygous carriers of this debilitating condition? (Heterozygous carriers have normal nose hair).

a. 1%

b. 2%

c. 4%

d. 18%

e. 80%

d. 18%

-q2 = 0.01, so q = 0.1 and p = 0.9. 2pq = 0.18

26. What is the best way to determine whether a trait is a quantitative trait, a single-locus Mendelian

trait, or has no genetic basis at all?

a. Look at one individual and see what their phenotype is.

b. Look at many individuals and see what their phenotype is.

c. Sequence the DNA for one individual for 10 randomly chosen genes, and calculate Ho.

d. Sequence the DNA for many individuals for 10 randomly chosen genes, and calculate Ho.

e. Do a standard breeding experiment with individuals of different phenotypes, and examine the

phenotypic distributions in the F1 and F2 generations.

e. Do a standard breeding experiment with individuals of different phenotypes, and examine the

phenotypic distributions in the F1 and F2 generations.

27. In thrushes (birds), the number of eggs a female can lay is under strong natural selection to increase.

It has been under natural selection in this same way for a long time. How much variation do we

expect to see now in the genes that control number of eggs? (Mating is random.)

a. Lots of variation: in every individual, all the genes that affect egg laying are probably

heterozygous. Example: AaBbCcDd...

b. High amounts of variation, but every individual may not be heterozygous at every locus.

c. No variation: in every individual, all the genes that affect egg laying are probably fixed in the

same way. Example: AABBCCDD...

d. No variation: in every individual, all the genes that affect egg laying are probably homozygous,

but in different ways. Example: some individuals are AAbbCCDD..., some aaBBCCdd..., some

AABBccdd..., etc.

e. There is no way to predict this.

c. No variation: in every individual, all the genes that affect egg laying are probably fixed in the

same way. Example: AABBCCDD...

28. In areas of Africa where malaria is prevalent, normal AA individuals have a fitness of 0.85 and

heterozygous AS individuals (with one sickle cell gene copy) have a fitness of 1.0. All homozygous

SS individuals have severe anemia and a fitness of 0. What is the equilibrium frequency of the

normal A allele in these areas?

a. 0

b. 0.54

c. 0.85

d. 0.87

e. 1.0

d. 0.87

-= 1 / (1+0.15)

29. In other areas of the world where malaria is not common, normal AA individuals have the highest

absolute fitness, and heterozygous AS individuals have lowered survivorship (fitness = 0.95).

Homozygous SS individuals with severe anemia have a fitness of 0.2. What is the equilibrium

frequency of the normal A allele in these areas?

a. 0

b. 0.06

c. 0.44

d. 0.94

e. 1.0

e. 1.0

-For a partial dominance model, the best allele is fixed at equilibrium. p = 1.0

30. You will find that the frequency of AA in zygotes is p2 when

a. the population is in Hardy Weinberg equilibrium

b. there is random mating

c. there is inbreeding

d. A and B only

e. A, B and C are all true

d. A and B only

31. Most natural selection models have both stable and unstable equilibria. In a model of full

dominance with 2 alleles, a population is sitting exactly on the unstable equilibrium. To move away

from this unstable equilibrium would require

a. no other microevolutionary forces. (Natural selection can easily move the population off of the

unstable equilibrium.)

b. genetic drift.

c. some inbreeding.

d. some outbreeding

e. a mutation

e. a mutation

-The unstable equilibrium is where there are no "A" alleles, only a. The only way to move it to the stable

equilibrium (fixation for A) is to have at least one mutation from a->A.

32. A model with both drift and gene flow ...

a. can be used for situations in which Hardy Weinberg equilibrium applies.

b. was first developed by Charles Darwin to explain descent with modification.

c. is used to estimate how much gene flow is actually occurring in natural populations.

d. shows that divergence among populations increases as gene flow increases.

e. explains why tomato soup with less salt costs more than regular tomato soup.

c. is used to estimate how much gene flow is actually occurring in natural populations.

-See lecture notes for answer c. Answer d is exactly the opposite: more gene flow means less

divergence.

2. Which population is polymorphic for this gene?

a. Lake Saimaa

b. Marine

c. both

d. neither

c. both

3. Pituitary dwarfism is a caused by a homozygous recessive condition at the growth hormone gene GH1. The forward rate of mutation from the normal gene to the mutant form is 1 x 10-6. The backward rate of mutation is so small that it can be ignored. If the frequency of the mutant allele is now 0.1000, what will it be in 1000 generations? Assume no natural selection or drift.

a. 0.0000

b. 0.0999

c. 0.1000

d. 0.1009

e. 0.8991

d. 0.1009

p = 0.9, q = 0.1

p1000 = 0.9 (1 - 1x10-6)

1000 = 0.8991

q1000 = 1 - p1000 = 0.1009

4. A brand new mutation has a 2% probability of eventually becoming fixed through the action of

genetic drift alone. How big is the population? (Assume that the species is diploid.)

a. 20

b. 25

c. 50

d. 100

e. 200

b. 25

-prob. of fixation = frequency of the allele. A new mutation has a frequency of 1/2N.

0.02 = 1/2N, so N = 25

5. Tall Guys Get the Girls: Short Men Less Likely to Marry, Have Kids by Rick Callahan, The Associated Press. Jan. 12, 2004 — If it seemed as if the tall guys got all the girls in high school, it wasn't your imagination. New research suggests taller men are more likely to marry and tend to have more children than short guys. What's behind the phenomenon — whether women prefer taller men or those men are simply more outgoing — is up for debate. But the numbers clearly stack up against shorter guys. Polish and British scientists studied the medical records of about 3,200 Polish men ages 25 to 60 and found that childless men were on average 1.2 inches shorter than men who had at least one child. Bachelors were about an inch shorter on average than married men. ... The findings were published in Thursday's issue of the journal Nature.

This is an example of

a. inbreeding

b. positive assortative mating

c. viability selection

d. sexual selection

e. gametic selection

d. sexual selection

-There is no information on nonrandom mating in this article. It states that taller men are more likely to mate. This is the definition of sexual selection.

6. The trait of interest in the last question (height) is a _______________ trait.

a. Mendelian

b. pleiotropic

c. quantitative

d. meristic

e. threshold

c. quantitative

-Height in humans is a quantitative, continuous trait.

7. In a population of sea bass, 80 randomly surveyed individuals have genotypes as follows. 15 are

DD, 36 are Dd and 29 are dd. Does this locus depart from Hardy-Weinberg frequencies? (For 1

degree of freedom χ2 > 3.84 is significant.)

a. Yes. χ2 = 323.5

b. Yes. χ2 = 11.6

c. No. χ2 = 0.41

d. No. χ2 = 0.08

e. No. χ2 = 0.0051

c. No. χ2 = 0.41

8. Which microevolutionary force is acting on the sea bass population from the last question?

a. inbreeding

b. negative assortative mating

c. mutation

d. natural selection (overdominance)

e. I accept the null hypothesis that none of these evolutionary forces are important.

e. I accept the null hypothesis that none of these evolutionary forces are important.

9. A large African population of humans has no sickle cell anemia alleles. Then there is a single

mutation in the gene pool from the normal allele to the sickle cell allele. (There are no more

mutations.) This is an population in which 1) malaria is common, 2) mating is random and 3) there is

no appreciable immigration or emigration. Based on what you know about sickle cell anemia from

lecture, what would you expect in patterns of diversity in newly fertilized zygotes?

a. Ho will reach a stable equilibrium between zero and one, and He will reach the same stable

equilibrium.

b. Ho will reach a stable equilibrium between zero and one, and He will reach a different stable

equilibrium between zero and one.

c. Ho will decrease to zero, and He will decrease to zero.

d. Ho will decrease to zero, and He will increase to one.

e. Ho will decrease to zero, and He will reach a stable equilibrium between zero and one.

a. Ho will reach a stable equilibrium between zero and one, and He will reach the same stable

equilibrium.

10. Many of the natural selection models have both stable and unstable equilibria. Imagine a model with

incomplete dominance, 2 alleles and high selection coefficients. A population is sitting very close to the stable equilibrium. To move the population steadily away from this stable equilibrium, generation after generation, would require

a. a single mutation.

b. genetic drift.

c. some inbreeding.

d. negative assortative mating.

e. None of these, because the population will almost certainly stay at or near the stable equilibrium.

e. None of these, because the population will almost certainly stay at or near the stable equilibrium.

11. Normal AA individuals have a relative fitness of 1.0, heterozygous Aa individuals have a relative

fitness of 0.95 and homozygous aa individuals have a relative fitness of 0.8. What are the selective

coefficients h and s in this model?

a. h = 0.95, s = 0.8

b. h = 0.05, s = 0.2

c. h = 0.05, s = 0.8

d. h = 0.25, s = 0.2

e. h = 0.062, s = 0.2

d. h = 0.25, s = 0.2

12. The model of natural selection in the previous question is

a. full dominance

b. partial dominance

c. overdominance

d. underdominance

e. Domino's pizza dominance

b. partial dominance

13. There are 12 AA individuals, 5 Aa individuals and 15 aa individuals. What is the frequency of the A

allele?

a. 0.266

b. 0.375

c. 0.453

d. 0.531

e. 0.906

c. 0.453

-= (24+5)/(24+10+30)

14. Which of the following is NOT true about a population in Hardy-Weinberg equilibrium?

a. allele frequencies do not change over time

b. genotype frequencies do not change over time

c. the population size is infinite

d. every gene copy makes an identical contribution to the gene pool in the next generation

e. mutations occur according to the one-way mutation model

e. mutations occur according to the one-way mutation model

15. Zygotes in a population are not in Hardy Weinberg frequencies. How can you distinguish between

inbreeding and assortative mating?

a. know the rules for mate choice in the adults

b. look at genotype frequencies at many genes on different chromosomes

c. examine mating pedigrees for many different individuals in the population

d. A and B only

e. A, B and C would all distinguish between inbreeding and assortative mating

e. A, B and C would all distinguish between inbreeding and assortative mating

16. Which of the following is false about mutations?

a. The two-way (forward-backward) mutation model does not have a stable equilibrium.

b. The one-way mutation model leads to a population with no heterozygosity.

c. Mutations cause dramatic allele frequency changes only after many thousands of generations.

d. Mutations provide the original source for all new alleles.

e. Mutation and selection can balance each other to maintain polymorphism

a. The two-way (forward-backward) mutation model does not have a stable equilibrium.

17. A monohybrid cross experiment is conducted. To determine whether the trait is controlled by one

gene or by many genes, it is most useful to study

a. the amount of variance in one of the two parental strains.

b. the difference between the mean values of the two parental strains.

c. the shape of both phenotypic distributions in the parental strains.

d. the phenotypic distribution in the F1 generation.

e. the phenotypic distribution in the F2 generation.