Question 1

Consider a population with a constant size,Nₑ = 5000,that experiences a mutation rate of 0.00005,with an initial F value of 0.15.What is the probability that two alleles selected at random from the offspring of this population will be identical by descent?
A)0
B)0.15
C)0.30
D)0.40
E)None of the above

Accepted Answer

The probability that two alleles are identical by descent is given by the inbreeding coefficient F, which is initially 0.15.

Question 2

In a diploid population,the threshold at which selection is likely to outweigh drift is when s (the selective advantage in this case)is
A)> 1/2Ne.
B)> Ne.
C)> 2Ne.
D)> 4Ne.
E)> Ne/4.

Accepted Answer

In a diploid population, selection is likely to outweigh genetic drift when the selective advantage (s) is greater than 1/(2Ne), where Ne is the effective population size.

Question 3

The neutral theory of molecular variation posits that most
A)mutations are neutral.
B)substitutions are neutral.
C)mutations are deleterious.
D)B and C
E)All of the above

Accepted Answer

The neutral theory of molecular evolution suggests that most genetic substitutions are neutral, meaning they do not affect an organism's fitness.

Question 4

The ancestor to the Hawaiian crickets in the genus Laupala originally colonized the oldest of the islands in the Hawaiian archipelago.As new islands were formed,crickets from the older island would colonize the younger island.Because members of this genus are flightless,these migration events were likely to be extremely rare and would include a small number of migrants.Nonselective differences in allele frequencies in this genus are likely due to
A)differences in mutation rate.
B)a founder event.
C)genetic drift subsequent to colonization.
D)A and C
E)B and C

Accepted Answer

The fact that crickets from older islands colonized the younger ones and that these crickets are flightless suggests that migration events were rare and involved only a small number of migrants. This scenario fits the definition of a founder event, where a small group of individuals establishes a new population with a limited set of genetic variations. As a result, the allele frequencies in the newly colonized population could be different from those in the source population due to genetic drift (random changes in allele frequencies), which reinforces the idea that choice E is the best answer. Mutations could play a role in generating new genetic variations, but they are not likely to be the primary driver of nonselective differences in allele frequencies in this genus.

Question 5

One consequence of genetic drift is
A)increasing heterozygosity in the population.
B)the maintenance of multiple alleles across long periods of time.
C)that populations diverge in terms of their allele frequencies.
D)that populations maintain the same set of alleles through time.
E)All of the above

Accepted Answer

Genetic drift can lead to random changes in allele frequencies within a population, causing populations to diverge in terms of their allele frequencies over time. The other choices are not necessarily consequences of genetic drift.

Question 6

Consider a collection of 50 distinct alleles,each at equal frequency in a population.The time before the first coalescent event will be shortest if
A)Ne = 100
B)Ne = 100,000,000
C)Ne = 100,000
D)Ne = 1,000,000,000.

Accepted Answer

The time before the first coalescent event is determined by the effective population size (Ne) of the population. The smaller the Ne, the shorter the time before coalescence. Therefore, choice A) Ne = 100, with a relatively small Ne, would result in the shortest time before the first coalescent event. Choices B), C), and D) with much larger Ne values would result in longer times before coalescence.

Question 7

If two randomly selected gene copies are sampled from a population of oak trees at a locus for which there is no selection,assortative mating,or migration,how many mutations would we expect these alleles to differ by?
A)2k
B)4k
C)2Ne
D)4Ne
E)4Nem

Accepted Answer

The answer of If two randomly selected gene copies are...

Question 8

The inbreeding effective population size is often lower than the census size of a population because of
A)inbreeding depression.
B)fluctuating population size.
C)uneven sex ratios.
D)B and C
E)All of the above

Accepted Answer

Inbreeding depression can reduce the effective population size by decreasing the survival and reproductive fitness of individuals. Fluctuating population size can also reduce effective population size because it increases the chance of genetic drift and loss of genetic diversity. Uneven sex ratios can limit the number of potential mates and decrease genetic diversity, further lowering the effective population size. Therefore, both B (fluctuating population size) and C (uneven sex ratios) are factors that can reduce the inbreeding effective population size.

Question 9

If it takes many generations for a collection of gene copies to coalesce to a single gene copy,we can infer that
A)Ne is small.
B)Ne is large.
C)there are few alleles in the population.
D)Ho will be small.
E)None of the above

Accepted Answer

It takes many generations for a collection of gene copies to coalesce to a single gene copy in large populations, indicating a large effective population size (Ne). In small populations, coalescence occurs relatively quickly. Therefore, option B is the best choice. Option A, C, and D are incorrect because a small Ne, few alleles, and low heterozygosity (Ho) lead to faster coalescence rather than slow coalescence.

Question 10

The figure above illustrates the
A)increase in homozygosity with time.
B)the effect of over-fishing on heterozygosity.
C)the decline of heterozygosity with time.
D)B and C
E)All of the above

Accepted Answer

The answer of  The figure above illustrates the
A)increase in...

Question 11

Refer to the figure above to answer the following question.Which of the following mutations to a codon is most likely to be selectively neutral?
A)UUG ® CUG
B)AUA ® AUG
C)AAC ® AAA
D)UGC ® UGA
E)AGC ® AGA

Accepted Answer

The answer of  Refer to the figure above to...

Question 12

The figure above demonstrates the
A)effects of genetic drift in small populations.
B)relationship between population size and the effects of selection.
C)relationship between population size and the effects of mutation.
D)relationship between population size and effective population size.
E)relationship between population size and the effects of migration.

Accepted Answer

The answer of  The figure above demonstrates the
A)effects of...

Question 13

Population bottlenecks occur when
A)a large number of genetically diverse individuals found a new population.
B)population size dramatically increases.
C)a consistently large population experiences a brief period of small size.
D)drift in consistently small populations become fixed for a single allele.
E)inbreeding is high.

Accepted Answer

Population bottlenecks occur when consistently large populations experience a brief period of small size. This can result in the loss of genetic diversity and potentially harmful genetic changes becoming fixed due to genetic drift.

Question 14

Consider a population with an effective size of 4000 and 32 segregating alleles.On average,how many generations would it take for all 32 alleles to coalesce to a single,ancestral allele?
A)32
B)128
C)1000
D)16000
E)Coalescence of all 32 alleles will never occur.

Accepted Answer

The expected time to coalescence for a pair of alleles is 2N generations, where N is the effective population size. Therefore, the expected time to coalesce for all 32 alleles is:

2N(1 + 1/2 + 1/3 + ... + 1/31)

Plugging in the given values:

2(4000)(1 + 1/2 + 1/3 + ... + 1/31) = 16000 generations

Therefore, the answer is D, 16000 generations.

Question 15

A rancher genotypes all of her 150 head of cattle.In her herd,25 are A₁A₁,75 are A₁A₂,and 50 are A₂A₂.Assuming there is random mating,no selection,no mutation,and no new cattle are introduced into the population,what is the probability that the A₁ allele will be fixed?
A)0
B)0.0127
C)0.4167
D)0.6588
E)1

Accepted Answer

The answer of A rancher genotypes all of her 150...

Question 16

The variable F is
A)the probability of two alleles being identical by descent.
B)a measurement used to quantify the loss of variation due to drift over time.
C)a measure of the degree of inbreeding.
D)A and B
E)All of the above

Accepted Answer

The variable F is all of the above. F is a commonly used measure of the degree of inbreeding, but it is also used to calculate the probability of two alleles being identical by descent and to quantify the loss of variation due to drift over time. Therefore, all of the choices (A, B, and C) are correct.

Question 17

A researcher examines a microsatellite locus in a wild population of D.melanogaster.He finds that in a sample of 50 individuals,20 different alleles are segregating.The best explanation for the presence of all of these alleles is
A)balancing selection.
B)mutation.
C)the neutral theory.
D)overdominance.
E)the law of large numbers.

Accepted Answer

The neutral theory suggests that most genetic variation is due to random drift of mutant alleles that are selectively neutral, which can explain the high number of alleles observed.

Question 18

Population bottlenecks can lead to the fixation or loss of alleles in otherwise large populations because the bottleneck
A)selectively eliminates or fixes alleles.
B)reduces the effective population size to close to the size of the bottleneck.
C)allows migrant alleles to overwhelm native alleles.
D)A and B
E)All of the above

Accepted Answer

A population bottleneck reduces the effective population size, increasing the impact of genetic drift, which can lead to the fixation or loss of alleles.

Question 19

Consider a population of size Nₑ with a new mutation that confers a fitness advantage of 1 + s.This new allele will be more likely to go to fixation due to selection if
A)Ne is large.
B)Ne is small.
C)s is small.
D)s is large.
E)A and D

Accepted Answer

A larger Ne means a greater genetic diversity that increases the potential for genetic drift to affect the fate of a new mutation, counterbalancing the positive effects of selection. In contrast, a smaller Ne increases the opportunity for genetic drift to decrease the frequency of the beneficial allele. Thus, a small Ne reduces the efficiency of selection in driving the new allele towards fixation. However, if the advantage of the new mutation is large (s is large), selection can override the effects of genetic drift even in small populations. Therefore, both options A (large Ne) and D (large s) increase the likelihood of a new advantageous allele to go to fixation in a population under natural selection.

Question 20

A founder event changes allele frequencies because
A)only a subset of genes in the original population are observed in the founder population.
B)of random sampling of alleles from the original population.
C)of the coalescent process.
D)A and B
E)All of the above

Accepted Answer

A founder event involves the establishment of a new population by a small subset of individuals from the original population. This subset may not represent the full range of genetic diversity present in the original population, leading to a decrease in genetic variation in the founder population (option A). Additionally, the random sampling of alleles from the original population during the establishment of the new population can result in changes in allele frequencies (option B). The coalescent process refers to the tracing of the ancestry of genes within a population, and is not directly related to founder events (option C). Therefore, the best choice is D, as both options A and B are valid explanations of how a founder event can change allele frequencies.

Quiz 8: Evolution in Finite Populations

Consider a population with a constant size,Nₑ = 5000,that experiences a mutation rate of 0.00005,with an initial F value of 0.15.What is the probability that two alleles selected at random from the offspring of this population will be identical by descent?

In a diploid population,the threshold at which selection is likely to outweigh drift is when s (the selective advantage in this case) is

The neutral theory of molecular variation posits that most

One consequence of genetic drift is

Consider a collection of 50 distinct alleles,each at equal frequency in a population.The time before the first coalescent event will be shortest if

If two randomly selected gene copies are sampled from a population of oak trees at a locus for which there is no selection,assortative mating,or migration,how many mutations would we expect these alleles to differ by?

The inbreeding effective population size is often lower than the census size of a population because of

If it takes many generations for a collection of gene copies to coalesce to a single gene copy,we can infer that

The figure above illustrates the

Refer to the figure above to answer the following question.Which of the following mutations to a codon is most likely to be selectively neutral?

The figure above demonstrates the

Population bottlenecks occur when

Consider a population with an effective size of 4000 and 32 segregating alleles.On average,how many generations would it take for all 32 alleles to coalesce to a single,ancestral allele?

A rancher genotypes all of her 150 head of cattle.In her herd,25 are A₁A₁,75 are A₁A₂,and 50 are A₂A₂.Assuming there is random mating,no selection,no mutation,and no new cattle are introduced into the population,what is the probability that the A₁ allele will be fixed?

The variable F is

A researcher examines a microsatellite locus in a wild population of D.melanogaster.He finds that in a sample of 50 individuals,20 different alleles are segregating.The best explanation for the presence of all of these alleles is

Population bottlenecks can lead to the fixation or loss of alleles in otherwise large populations because the bottleneck

Consider a population of size Nₑ with a new mutation that confers a fitness advantage of 1 + s.This new allele will be more likely to go to fixation due to selection if

A founder event changes allele frequencies because