Deck 9: Evolution at Multiple Loci

Question 1

Which of the following processes that can create linkage disequilibrium is illustrated in the figure below?

A)Drift
B)Selection
C)Mutation
D)Migration
E)All of the above

Answer 1

D

Question 2

If the value of linkage disequilibrium (D)is equal to -0.25,one can infer that the alleles are

A)in repulsion.
B)in coupling.
C)in linkage disequilibrium.
D)A and C
E)None of the above

Answer 2

D

Question 3

A haplotype is

A)all of the alleles at a single locus.
B)a product of epistasis.
C)a set of alleles at different loci along a chromosome.
D)all of the alleles in a population.
E)None of the above

Answer 3

C

Question 4

Selection can generate novel phenotypes by

A)drift causing the creation of a new phenotype.
B)increasing the probability of novel allele combinations.
C)linkage disequilibrium and selective sweeps.
D)B and C
E)None of the above

Question 5

The observation of an offspring phenotype outside of the range of parental phenotypes is most likely due to

A)additive genetic effects.
B)mutation.
C)selection.
D)latent variation.
E)C and D

Question 6

In the figure above,each new line represents the frequency of a new beneficial mutation.The figure describes the process of

A)selective sweeps.
B)periodic selection.
C)genetic hitchhiking.
D)background selection.
E)A and B

Question 7

In the figure below,the grey boxes represent the offspring of parents that are heterozygous at locus 1 (Aa)and locus 2 (Bb).Which of the grey boxes represent repulsion double heterozygote offspring?

A)Light grey
B)Medium grey
C)Dark grey
D)B and C
E)All of the above

Question 8

The statistical association of alleles at different loci is referred to as

A)physical linkage.
B)haplotypes.
C)epistasis.
D)linkage equilibrium.
E)linkage disequilibrium.

Question 9

The following figure demonstrates the genotypic adaptive landscape for bacteria growing in media without antibiotics.The height of the bars associated with a genotype indicates the fitness of that genotype.The R allele confers resistance to antibiotics,and the C allele compensates for the loss of fitness that the R allele confers in the absence of antibiotics.The rc haplotype lacks both compensation and resistance.Based on this landscape,why are resistance and compensation unlikely to be lost even in the absence of antibiotics?

A)A lack of mutation will prevent the haplotypes from changing.
B)Epistasis will maintain haplotype frequencies.
C)Haplotype frequencies do not change in Hardy-Weinberg populations.
D)RC populations are stuck on a local maximum.
E)Bacteria evolve slowly.

Question 10

Understanding phenotype-genotype relationships is difficult because of

A)pleiotropy.
B)dominance.
C)epistasis.
D)A and C
E)All of the above

Question 11

What two major concepts in biology were unified in the middle of the twentieth century?

A)Natural selection and drift
B)Discontinuous and continuous variation
C)Mutation and migration
D)Natural selection and Mendelian genetics
E)Population genetics and quantitative genetics

Question 12

Consider a population with two loci (A,B),each with two alleles (A,a; B,b).What are the haplotype frequencies in this population if the allele frequencies are A = 0.5,a = 0.5,B = 0.7,b = 0.3?

A)AB = 0.35, Ab = 0.15, aB = 0.35, ab = 0.15
B)AB = 0.45, Ab = 0.05, aB = 0.25, ab = 0.25
C)AB = 0.4, Ab = 0.1, aB = 0.3, ab = 0.2
D)AB = 0.125, Ab = 0.25, aB = 0.25, ab = 0.125
E)Cannot be determined based on the information provided

Question 13

In the figure above,the population indicated by the dots

A)has a high fitness.
B)exhibits two distinct morphs
C)is experiencing background selection.
D)is experiencing drift.
E)is in equilibrium.

Question 14

In the figure above,a new beneficial allele,B,arises on a chromosome containing the ordered loci A,B,C,D,and E,depicted in the top panel.After reproduction,those chromosomes possessing the B allele increase in frequency.Over time,recombination breaks up the association of the B allele with the A,C,D,and E alleles.Assuming that the five loci are spaced evenly along the chromosome,the first pair of allele combinations to be broken up will be

A)B and A.
B)B and C.
C)B and D.
D)B and E.
E)All alleles will break up at an equal rate

Question 15

What is the largest possible value that linkage disequilibrium can reach if all allele frequencies are 0.5?

A)0.25
B)0.5
C)0.75
D)1
E)None of the above

Question 16

The rediscovery of Mendelian inheritance caused increased scrutiny of Darwin's theory of natural selection because of an apparent conflict in the two concepts.This conflict was based on the observation that Darwin focused on continuous traits,whereas Mendelian genetics deals with

A)discrete characters.
B)alleles.
C)flowers.
D)genotypes.
E)All of the above

Question 17

The figure above demonstrates that Hardy-Weinberg frequencies are

A)uniquely determined by allele frequencies.
B)determined by haplotype frequencies.
C)depend on the recombination rate.
D)All of the above
E)None of the above

Question 18

Which of the following can generate linkage disequilibrium?

A)Drift
B)Selection
C)Mutation
D)Migration
E)All of the above

Question 19

Assuming the value of linkage disequilibrium (D)is positive,recombination will generate

A)more repulsion pairs.
B)more coupling pairs.
C)no change, since recombination does not change expected haplotype frequencies.
D)an increase in D.
E)None of the above

Question 20

Consider two loci on a single chromosome.These loci

A)have alleles that will always segregate together.
B)are physically linked.
C)are in linkage disequilibrium.
D)interact with each other.
E)will be broken up during recombination.

Question 21

In a population of dragonflies,wing structure is determined by two loci (A,B),each with two alleles (Aa,Bb).Abnormal wings are produced in aa individuals unless they possess at least one B allele.This is an example of

Question 22

Why would we expect genotypic adaptive landscapes to have rugged contours?

Question 23

A study of susceptibility to major depressive disorder in monozygotic twins separated at birth revealed that the broad-sense heritability of this trait is 0.10,and its total phenotypic variance is 0.25.What is the variance of the genotypic value of this disorder? Show your work.

Question 24

Multiple drug-resistant Staphylococcus aureus (MRSA)is a bacterium that has developed resistance to a wide range of antibiotics.Its resistance to penicillin,methicillin,and oxacillin is a result of the serial use of these antibiotics,which created a selective environment that favored resistance to the drug being used at the time.This resistance provides the bacteria with the ability to thrive in an environment with standard antibiotics,thereby making it a dangerous human health hazard.Why would one expect MRSA to retain penicillin resistance even if this antibiotic is rarely used?

Question 25

A species of lotus produces a nearly continuous spectrum of flower colors,ranging from white to deep red.The color of the flower is determined by 10 loci,each with two codominant alleles.What concept does this example illustrate?

Question 26

Without using mathematical symbols,explain the difference between broad- and narrow-sense heritability,including why one is more relevant to evolutionary studies.

Question 27

A researcher tracks the escape behavior of a population of squirrels on campus across two generations.When she plots the escape behavior of the offspring generation against the parental behavior,she notes that the offspring's behavior exactly matches the parental behavior.Nonetheless,the narrow-sense heritability equals zero.How can the heritability equal zero in this example?

A)The additive genetic variance equals zero.
B)All the escape behavior alleles are fixed in the population.
C)There is no phenotypic variation.
D)A and B
E)All of the above

Question 28

If recombination between locus A and locus B is 0.15,and the initial value of linkage disequilibrium is 0.20,what will the value of linkage disequilibrium be after one generation of recombination? Show your work.

Question 29

Texas longhorn cattle have been bred to increase the tip to tip width of their horns,and the heritability of this trait has been well studied by Professor David Hillis at the University of Texas,Austin.In the current generation,the mean horn length is 52 inches.If only a subset of this population,with a mean horn length of 61 inches,are allowed to reproduce,and the narrow-sense heritability of this trait = 0.2,what is the expected horn length in the offspring generation?

A)~1.8 inches
B)~9 inches
C)~54 inches
D)~61 inches
E)Cannot be determined based on the information provided

Question 30

In Lake Malawi cichlid fish,one can observe two color variants,Black Barred (BB)and Orange Blotch (OB).Sex in these fish is not determined by a sex chromosome but by a gene on an autosome,which produces either males or females.Both of these phenotypes are controlled by one biallelic locus each.OB females have a selective advantage in terms of their survivability: The OB phenotype allows females to blend into their background.OB males have a selective disadvantage because their reproductive coloration is disrupted and they have little mating success.How would this process influence the association of alleles at the color locus and sex determining locus?

Question 31

The figure below describes the percent oil content in corn from different generations.What is the expected slope of a parent-offspring regression for corn oil content?

A)0.69
B)1.6
C)2.1
D)2.5
E)Cannot be determined based on the information provided

Question 32

Consider two microsatellite loci (A,B)each with two alleles determined by the number of repeats of the microsatellite motif (A = 15 or 17; B = 27 or 31).You genotype an individual in this population and determine that its haplotype is 15/27 and 15/27.Are these alleles in coupling and/or repulsion? Explain your answer.

Question 33

In the figure below,what does the straight line indicate?

A)The broad-sense heritability
B)The narrow-sense heritability
C)The norm of reaction of nocturnal restlessness
D)None of the above
E)All of the above

Question 34

Genotypic adaptive landscapes may better represent true adaptive landscapes than phenotypic adaptive landscapes when

A)single mutations can have a large effect on the phenotype.
B)phenotypic landscapes are hard to mathematically model.
C)phenotypic landscapes do not account for drift.
D)genotypic landscapes are easier to visualize.
E)genotypic landscapes are smooth.

Question 35

Explain why one cannot compare the estimated heritability of intelligence tests from different populations from the United States.

Question 36

Consider two loci (A,B)each with two alleles (Aa,Bb).The frequency (f)of A is known to be 0.3,the frequency (f)of b is known to be 0.25,and the coefficient of linkage disequilibrium (D)between loci A and B is known to be 0.15.What is the expected haplotype frequency of hₐB? Please show your work.

Question 37

In quantitative genetic terms,a phenotypic value can be expressed as

A)dominance and recessiveness.
B)epistasis and pleiotropy.
C)genotypic value and environmental deviation.
D)A and B
E)All of the above

Question 38

Narrow-sense heritability is defined as the total

A)genetic variation divided by the total phenotypic variation.
B)additive genetic variation divided by the total phenotypic variation.
C)dominance genetic variation divided by the total phenotypic variation.
D)additive genetic variation divided by the total dominance variation.
E)epistatic genetic variation divided by the total dominance variation.

Question 39

Explain why a population may never reach its most fit phenotype.