Question 1

Broad-sense heritability is defined as the ________ genetic variation divided by the ________ variation.
A) total; total phenotypic
B) additive; total phenotypic
C) dominance; total phenotypic
D) additive; total dominance

Accepted Answer

Broad-sense heritability takes into account all sources of genetic variation, including additive, dominance, and epistatic effects, and divides this by the total phenotypic variation observed in a population. Therefore, the correct choice is A, as it reflects the definition of broad-sense heritability.

Question 2

When the alleles at two or more loci interact in nonadditive ways, we refer to this as
A) pleiotropy.
B) epistasis.
C) physical linkage.
D) linkage equilibrium.

Accepted Answer

The interaction of alleles at different loci in nonadditive ways is referred to as epistasis. Pleiotropy refers to the phenomenon in which a single gene influences multiple, seemingly unrelated traits. Physical linkage refers to the location of two or more genes on the same chromosome, while linkage equilibrium refers to the random association of alleles at different loci.

Question 3

In a population of dragonflies, wing structure is determined by two loci (A, B), each with two alleles (A and a, B and b). Abnormal wings are produced in aa individuals unless they possess at least one B allele. This is an example of what evolutionary phenomenon?
A) epistasis
B) linkage equilibrium
C) physical linkage
D) latent variation

Accepted Answer

The phenomenon described is an example of epistasis, which occurs when the expression of one gene affects the expression of another gene. In this case, the expression of the B gene affects the expression of the A gene, so that individuals with certain combinations of alleles at these loci will have abnormal wing structures.

Question 4

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.

Accepted Answer

The answer of Consider two microsatellite loci (A, B), each...

Question 5

What is narrow-sense heritability and why is it a useful metric?

Accepted Answer

The answer of What is narrow-sense heritability and why is...

Question 6

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?

Accepted Answer

The answer of In Lake Malawi cichlid fish, one can...

Question 7

An individual mapped within an adaptive landscape as a point located in a fitness valley would be characterized as having
A) high fitness.
B) low fitness.
C) a fitness peak.
D) a single-peaked landscape.

Accepted Answer

A fitness valley is characterized by low fitness. It is a depression within the landscape where organisms with certain traits have lower fitness than individuals with other traits. Therefore, an individual mapped within an adaptive landscape as a point located in a fitness valley would be characterized as having low fitness.

Question 8

Which of the following reflects the degree to which offspring resemble their parents in a population?
A) narrow-sense heritability
B) broad-sense heritability
C) selection differential
D) dominance

Accepted Answer

Narrow-sense heritability measures the proportion of phenotypic variance that is attributable to additive genetic variance, which directly affects the resemblance between parents and offspring.

Question 9

Which of the following processes causes a neutral allele to increase in frequency because it is linked to an allele under selection?
A) mutation
B) genetic drift
C) genetic hitchhiking
D) background selection

Accepted Answer

Genetic hitchhiking, also known as genetic draft or selective sweep, occurs when a neutral allele that is physically linked to an allele under selection (such as a beneficial mutation) increases in frequency along with the selected allele. This is because the neutral allele is inadvertently "dragged along" as the selected allele spreads through the population. The neutral allele can then become more common even if it has no direct benefit or detriment to fitness.

Question 10

If we are interested in the A, B, and C loci of a diploid organism, which of the following would be a possible haplotype?
A) ABc
B) AABbcc
C) Aa
D) AAcc

Accepted Answer

A haplotype refers to a combination of alleles at multiple loci that are transmitted together on the same chromosome. Since diploid organisms have two sets of chromosomes, one from each parent, a haplotype would reflect a single set of these alleles. Option A, ABc, correctly represents alleles from a single set of chromosomes for loci A, B, and C. Options B, C, and D include representations that either mix alleles from both sets of chromosomes or do not include all the specified loci.

Question 11

Which of the following does NOT represent a way in which genotype and phenotype can interact?
A) pleiotropy
B) epistasis
C) norms of reaction
D) physical linkage

Accepted Answer

Physical linkage refers to the physical proximity of two genes on a chromosome, and how their location affects their inheritance and expression. It does not directly involve the interaction between genotype and phenotype. Pleiotropy, epistasis, and norms of reaction are all ways in which genotype and phenotype can interact.

Question 12

The phenotypic variation created by random chance events during the process of an organism's development is called
A) mutation.
B) drift.
C) acclimation.
D) developmental noise.

Accepted Answer

Developmental noise refers to the random variation that occurs during development and can result in phenotypic differences between individuals. This variation is not the result of genetic mutations or natural selection, but rather chance events that occur during development. Drift refers to changes in allele frequencies in a population due to random chance events, while acclimation refers to an individual's ability to adjust to changes in their environment.

Question 13

Consider two loci (A, B), each with two alleles (A and a, B and b, respectively). The frequency (f) of A is known to be 0.30, 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 h_aB? Use the equation D =f_af_B -h_aB to solve. Show your work.

Accepted Answer

The answer of Consider two loci (A, B), each with...

Question 14

Using the concept of adaptive landscapes, explain why a population may never reach its most fit phenotype.

Accepted Answer

The answer of Using the concept of adaptive landscapes, explain...

Question 15

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

Accepted Answer

The answer of If recombination between locus A and locus...

Question 16

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 might one expect MRSA to retain penicillin resistance even if this antibiotic is rarely used?

Accepted Answer

The answer of Multiple drug-resistant Staphylococcus aureus (MRSA) is a...

Question 17

When the alleles at all loci of interest occur independently, what will the value of linkage disequilibrium (D) be?
A) 1
B) 0
C) -0.25
D) 0.25

Accepted Answer

Linkage disequilibrium (D) is the measure of non-random association between alleles at two or more loci. When the alleles at all loci of interest occur independently, there is no association between them, hence D=0.

Question 18

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 one.
B) All the escape behavior alleles are fixed in the population.
C) Phenotypes vary widely between generations.
D) Escape behavior is controlled by a rare recessive allele.

Accepted Answer

Heritability measures the proportion of variation in a trait that is due to genetic factors. If all the individuals in the population have the same genotype (i.e., fixed alleles), there is no genetic variation, and therefore, the heritability is zero. Therefore, even though the offspring's behavior matches the parental behavior, if there is no genetic variation, the heritability will still be zero.

Question 19

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?

Accepted Answer

The answer of A species of lotus produces a nearly...

Question 20

In the figure depicting heritability of migratory timing in the blackcap warbler, 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) the response to selection

Accepted Answer

The straight line in the figure represents the narrow-sense heritability, which is the proportion of phenotypic variance that is due to additive genetic variance. This means that genetic factors play a significant role in determining migratory timing in blackcap warblers. The broad-sense heritability includes all sources of genetic variation, including dominant and epistatic effects, which are not accounted for in the narrow-sense heritability. The norm of reaction of nocturnal restlessness refers to the range of phenotypic expressions of a particular genotype in different environments, which is not shown in this figure. The response to selection is the change in average trait value over time due to differential survival or reproduction of individuals with certain traits, which is not directly indicated by this figure.

Quiz 9: Evolution at Multiple Loci

Broad-sense heritability is defined as the genetic variation divided by the variation.

When the alleles at two or more loci interact in nonadditive ways, we refer to this as

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

What is narrow-sense heritability and why is it a useful metric?

An individual mapped within an adaptive landscape as a point located in a fitness valley would be characterized as having

Which of the following reflects the degree to which offspring resemble their parents in a population?

Which of the following processes causes a neutral allele to increase in frequency because it is linked to an allele under selection?

If we are interested in the A, B, and C loci of a diploid organism, which of the following would be a possible haplotype?

Which of the following does NOT represent a way in which genotype and phenotype can interact?

The phenotypic variation created by random chance events during the process of an organism's development is called

Using the concept of adaptive landscapes, explain why a population may never reach its most fit phenotype.

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

When the alleles at all loci of interest occur independently, what will the value of linkage disequilibrium (D) be?

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?

In the figure depicting heritability of migratory timing in the blackcap warbler, what does the straight line indicate?