Which of the following assumptions does not underlie Kimura's neutral theory of molecular evolution?
a. High amounts of genetic variation segregate in natural populations.
b. Evolutionary changes at the molecular level occur at a relatively constant rate.
c. Advantageous mutations occur often, and many fixation events are due to positive selection.
d. Mutation rates affect rates of substitution.
e. Deleterious alleles are eliminated by means of (purifying) natural selection.
Advantageous mutations occur often, and many fixation events are due to positive selection.
A set of 107 experimental populations of Drosophila melanogaster were maintained at a population size of 16 individuals for multiple generations. In each population, the initial frequencies of bw75 and bw alleles were equal. After 19 generations, the bw75 was fixed in 28 populations and lost in 30 populations. Results are shown in the figure below.
These results suggest that
a. both alleles are neutral, and fixation events were due to genetic drift.
b. the bw75 allele has a higher fitness than the bw allele, and fixation events were due to genetic drift.
c. the bw75 allele has a higher fitness than the bw allele, and fixation events were due to natural selection.
d. both alleles are neutral, and fixation events were due to natural selection.
e. a population size of 16 individuals is too small to display the effects of genetic drift.
both alleles are neutral, and fixation events were due to genetic drift.
FST is a measure of population differentiation. An equation exists for the equilibrium FST when the forces of drift and mutation counteract each other. Which of the following statements about this equation is false?
a. If rates of migration are high, then at equilibrium, FST will be low.
b. Gene flow causes demes to differ, while genetic drift causes demes to be similar.
c. FST levels can be used to estimate migration rates.
d. If rates of migration are low, then at equilibrium, FST will be high.
e. If population sizes are large, FST will be low.
Gene flow causes demes to differ, while genetic drift causes demes to be similar.
In the late eighteenth century, a typhoon swept through the Pacific atoll of Pingelap, leaving approximately 20 survivors. A large percentage of the present-day inhabitants of Pingelap are color blind. One can conclude, therefore, that the population experienced a
b. speciation event.
c. selective sweep.
Which of the following is not a reason that an effective population size can be smaller than the actual population size?
a. There are different numbers of males and females in the population.
b. Every individual produces exactly two offspring.
c. Generations overlap.
d. There is natural selection (a high variance in the number of offspring).
e. Population size fluctuates.
Every individual produces exactly two offspring
Which of the following is not a good explanation for why rates of molecular evolution vary between lineages?
a. Genes evolve more slowly in organisms with long generation times.
b. Mutation rates vary for organisms with different metabolic rates.
c. Natural selection acts equally on sequence variation in all parts of the genome.
d. Variation in effective population sizes leads to variation in the rate that genetic differences accumulate.
e. All of the above are good explanations.
Natural selection acts equally on sequence variation in all parts of the genome.
A rodent species has a population in one area of 100,000 individuals, and the per-gene mutation rate is 10-6. The average heterozygosity of this population is 0.0909. Another population of the same species has twice as many individuals (200,000). Assuming equilibrium, what would you expect the average heterozygosity of the second population species to be?
Two alleles (A and B) segregate at a locus. Assuming that no stabilizing forces exist, the A allele will eventually be
b. either lost or found.
d. either fixed or broken.
e. either lost or fixed.
either lost or fixed.
Which of the following statements about genetic drift is true?
a. Mildly disadvantageous alleles can sometimes increase in frequency, due to genetic drift.
b. Evolution by random genetic drift proceeds faster in large populations than in small populations.
c. Linkage disequilibrium cannot occur, because of genetic drift.
d. New mutations that are neutral are less likely to be fixed in small populations than in large populations.
e. Heterozygosity is unaffected by genetic drift.
Mildly disadvantageous alleles can sometimes increase in frequency, due to genetic drift.
Consider a hypothetical locus with two segregating alleles (A and B). Population size is small, mutation is absent, and neither of the two alleles has a selective advantage. Which of the following is likely to occur after a long period of time (many generations)?
a. Allele frequencies will change over time, but both alleles will remain.
b. Allele frequencies will remain constant.
c. Balancing selection will maintain both alleles.
d. Allele frequencies will cycle over time.
e. The population will eventually become monomorphic for one of the two alleles.
The population will eventually become monomorphic for one of the two alleles.
Human mtDNA lineages coalesced over a hundred thousand years ago (156 to 250 Kya) in a putative individual who has been dubbed "mitochondrial Eve." What does this name mean?
a. The human population at the time had only one female.
b. The name "Eve" first appeared in the historical record over a hundred thousand years ago.
c. Genetic drift does not affect coalescent times.
d. There are many origins for modern Homo sapiens.
e. Other females lived at the time, but their mtDNA is absent from today's population.
Other females lived at the time, but their mtDNA is absent from today's population.
Natural selection and genetic drift are the two most important causes of evolutionary change. How do they differ?
a. Only natural selection can change the frequencies of alleles in a population.
b. Genetic drift is nonadaptive; it changes allele frequency without regard to fitness.
c. Only genetic drift has been observed in populations of finite size.
d. Natural selection involves a population moving toward a goal, while genetic drift is not directed.
e. Natural selection focuses on the survival of individuals, while genetic drift refers to which individuals actually reproduce
Genetic drift is nonadaptive; it changes allele frequency without regard to fitness.
A striking conclusion of the neutral theory is that the rate of fixation of neutral mutations is equal to the mutation rate (u0). Why?
a. Different allele copies have different probabilities of fixation.
b. Mutation rates are orders of magnitude greater than other parameters in evolutionary biology.
c. Genetic drift does not affect the probability of fixation.
d. The number of new mutations in a population per generation, multiplied by the probability that any one allele copy will be fixed, is equal to u0.
e. Functional constraints do not affect the rate of evolution.
The number of new mutations in a population per generation, multiplied by the probability that any one allele copy will be fixed, is equal to u0.
A small population of three-spined stickleback fish lives in an Alaskan lake. Two alleles segregate at a neutral locus (A and B). The allele frequency of the A allele is 0.78. Which of the following allele frequencies would most likely be found in the next generation?
Very little genetic variation exists for populations of the northern elephant seal (Mirounga angustirostris). While 30,000 individuals exist today, in the 1890s hunting reduced the population size to about 20 individuals. What is the reason for such low genetic variation in this species?
a. The mating system of elephant seals leads to a low effective population size.
b. Hunting in the 1890s selected for clever seals.
c. The population experienced a bottleneck.
d. Both a and b
e. Both a and c
Both a and c: The mating system of elephant seals leads to a low effective population size and the population experienced a bottleneck.
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