Deck 20: Evolution and Medicine

Question 1

Which of the following is a telltale sign that a cell is infected by RNA viruses?

A)It is dividing slower than uninfected cells.
B)It contains long segments of double-stranded RNA.
C)Its apoptosis pathway is up-regulated.
D)It has a lower rate of protein synthesis.

Answer 1

B

Question 2

Under which of the following evolutionary explanations for disease does the antagonistic pleiotropy hypothesis for aging fall?

A)Natural selection has not had time to catch up with environmental changes.
B)Natural selection lacks foresight; we are stuck with historically contingent relics of the past.
C)Natural selection favors reproductive success, even at the expense of vulnerability to disease.
D)Some disease symptoms, though unpleasant, are actually beneficial.

Answer 2

C

Question 3

Which of the following hypothetical viruses would likely show a "cactus-shaped" population phylogeny?

A)A mutualistic virus that is vertically transmitted
B)A highly virulent virus, like Ebola, that kills its host before the build-up of any immunity
C)A highly virulent virus that results in life-long immunity and that can only infect naïve individuals (e.g., young children) that have never encountered any of the virus's strains
D)A virus that can reinfect previously infected hosts via escape mutants

Answer 3

D

Question 4

Plants do not have a germ line and gametes are derived from cell lines that are also responsible for the growth of the organism.Can the disposable soma hypothesis be applied to plants?

A)Yes, trade-offs between reproduction and repair are still possible.
B)Yes, plants have a much higher physiological tolerance for the effects of mutations.
C)No, the distinction between somatic cells and germ line is at the heart of the hypothesis.
D)No, plants do not produce eggs or sperm but gametophytes that represent an additional generation.

Question 5

.Ackermann and colleagues (2003)investigated senescence in bacteria.What do the following results demonstrate and why are they surprising given evolutionary theory on aging?

A)Bacteria do not senesce. Every organism should show trade-offs between fitness and longevity.
B)Bacteria do not senesce. Extrinsic mortality is not constant throughout the life of a bacterial cell.
C)Bacteria do senesce. Pleiotropy is the rare exception in simple bacterial genomes.
D)Bacteria do senesce. Cell propagation and reproduction are the same in bacteria.

Question 6

The figure below shows the effect of an antagonistic pleiotropic mutation (A).What would be the effect of a mutation (B)that delayed the onset of reproduction without changing the survival curve?

A)Genotypes carrying A and B would have a higher fitness than genotypes carrying A without B.
B)Genotypes carrying A and B would have a lower fitness than genotypes carrying A without B.
C)B would not have any effect on the fitness of individuals with A.
D)We cannot determine the effect of B without the survival curve for individuals that are wild-type at the locus affected by A.

Question 7

Many wild mushrooms make delicious food,but some are highly toxic and can result in a fatal meal.Apply the principle of asymmetric harm to mushroom identification,and recommend a strategy for mushroom identifiers.

Question 8

Which of the following are strategies with which vertebrate hosts counteract the asymmetries between most pathogens and their hosts?

A)Somatic mutation and lateral gene transfer between immune system cells
B)Somatic recombination and restriction endonucleases
C)Somatic mutation and recombination
D)Rapid population growth of host organisms and clonal expansion

Question 9

Under which hypothesis may pathogens ultimately be responsible for the evolution of sexual reproduction in multicellular organisms?

A)Good genes hypothesis
C)Mutation accumulation hypothesis
B)Red Queen hypothesis
D)Rate-of-living hypothesis

Question 10

Sickle cell anemia (a serious heritable disease)appears to be maintained via balancing selection in some African populations because heterozygous carriers for the fully recessive disease allele are less affected by malaria parasites.Is this a case of antagonistic pleiotropy?

A)Yes, the same allele has positive effects on one trait and negative effects on another trait.
B)Yes, wild-type and sickle cell alleles have antagonistic effects.
C)No, there is no time lag between the two traits (i.e., as in early vs. late acting).
D)No, it involves a dominance interaction between the wild-type and the sickle cell allele.

Question 11

Which of the following is an example of a trade-off imposed on an organism that results in a medical problem?

A)Patients who became infected by a novel flu strain had had no previous exposure to that particular strain.
B)Sturdier bones would prevent fractures but would also slow down organisms mobility.
C)The crossing of air and food pathways in humans increases the risk of choking.
D)Recent changes in human diet contribute to metabolic diseases.

Question 12

What is the likely phylogenetic explanation for the crossing of food and air pathways in humans?

A)A connection between the two previously separated pathways evolved to allow for an alternative air intake in case of a "stuffy nose."
B)Lungs evolved from pouches in the digestive system.
C)Access to odor receptors in the nose allowed for assessing food quality before swallowing.
D)A connection between both pathways allowed for a more efficient swallowing mechanism.

Question 13

What two main factors are responsible for the asymmetry in the coevolutionary arms race between microbial pathogens and their multicellular hosts?

Question 14

Explain how ectothermic animals can produce a fever response.Limit your answer to one sentence.

Question 15

Define pathogen-associated molecular patterns (PAMPs),and explain why they are crucial to our body's immune response against pathogens.Limit your answer to two sentences.

Question 16

Why is there no lifelong vaccine protection against flu as there is by a measles vaccine?

A)The variety of flu strains is too great to be captured by a single vaccine.
B)Flu can escape host immunity by evolving new variants that re-infect hosts.
C)The flu is too virulent to effectively vaccinate against.
D)The antigenic memory against flu has a short half-life.

Question 17

Which of the following represents a similarity between the evolution of tumors and the vertebrate immune response?

A)Both involve somatic mutations.
B)Both involve sexual reproduction.
C)Both can be examined using the Hardy-Weinberg principle.
D)Genetic drift is negligible in both systems.

Question 18

Patients with severe bacterial sepsis who develop a fever have higher survival rates than those who do not develop a fever.Does this observation provide causative evidence for the beneficial role of fever in fighting infections?

A)Yes, patients who develop a fever will have a higher mean fitness.
B)Yes, developing a fever is correlated with a strong immune system.
C)No, the disease in nonfever patients may have been too severe to allow the body to develop a fever.
D)No, fever has been shown by other studies to be inconsequential in fighting infections.

Question 19

Which part of the immune system's "learning system" is responsible for maintaining life-long immunity against measles after a measles infection?

A)Somatic recombination
C)Affinity maturation
B)Clonal expansion
D)Retention of responding cells

Question 20

Ask a question about fever at each of Tinbergen's four levels (1,2,3,and 4)of explanation.Limit your answer to one sentence for each level.

Question 21

Name three methods that pathogens use to subvert their host's immune system.

Question 22

Which of the two viral phylogenies below shows the signature of a recent,rapid population expansion? Justify your answer in one or two sentences.

Question 23

What combination of the characteristics of Huntington's disease puzzled J.B.S.Haldane?

Question 24

Figures A and B show the effect of an early- and a late-acting mutation on the lifetime fitness of individuals.Based on the graphs,how would you determine which of the two mutations had a greater effect on lifetime fitness? Limit your answer to one sentence.

Question 25

Imagine two populations of snails that are polymorphic for sexual reproduction.In each of the two populations,several asexual lineages and a panmictic,sexually reproducing subpopulation of snails are living in the same environment.Several years ago,a new pathogen was detected in the first population.This pathogen is transmitted predominantly between parents and their offspring,but on occasion,it is also transmitted horizontally between unrelated individuals.The pathogen is now infecting both sexual and asexual individuals.Since the introduction of the pathogen,the formerly stable ratio of sexual to asexual snails has shifted significantly in favor of the sexually reproducing individuals.At the same time,the second population became infected with a pathogen that is almost always transmitted horizontally.In the second population,no shift in the ratio of sexuals to asexuals has been observed.Speculate on why the difference in transmission between the two pathogens may have shifted the proportion of sexual reproduction in the first but not in the second population.Limit your answer to one or two sentences.

Question 26

Individuals of a certain tree species experience a markedly higher mortality rate at age 200 and beyond.Name two other changes you would expect in 200-year-old trees if this increase in mortality was accompanied by senescence.

Question 27

Can you think of examples,similar to the crossing pathways of food and air,in human anatomy or physiology that represent an "imperfect design" due to evolutionary history?