Contemporary Issues in Biology Exam 4 - 139 Questions and
Answers Already Graded A+ Premium Exam Tested And
Verified
Subject Area Contemporary Issues in Biology
Description This exam covers advanced topics in contemporary biology, including
CRISPR-Cas9 gene editing, synthetic biology, microbiome research, epigenetics,
prion biology, RNA interference, horizontal gene transfer, climate change impacts
on evolution, and emerging infectious diseases. It emphasizes conceptual
understanding, experimental design, and data interpretation at the level expected
of top-tier US university students.
Expected Grade A+
Total Questions 139
Duration 3 hours
Learning Outcomes 1. Critically evaluate the ethical and technical limitations of CRISPR-Cas9 gene
drives
2. Analyze the ecological and evolutionary consequences of horizontal gene
transfer in prokaryotes
3. Interpret epigenetic inheritance patterns and their implications for
transgenerational effects
4. Apply knowledge of prion propagation mechanisms to understand
neurodegenerative diseases
5. Design experiments to test hypotheses in synthetic biology and RNA
interference
6. Assess the impact of climate change on species adaptation and extinction risk
7. Evaluate strategies for emerging infectious disease surveillance and control
Accreditation This exam adheres to the rigorous standards of Ivy League and R1 research
universities, requiring deep reasoning and synthesis across multiple biological
disciplines.
Page 1
,1. A research team proposes using a CRISPR-Cas9 gene drive to suppress a
population of invasive rodents on an island. Which of the following is the most
significant ecological risk that must be evaluated before release?
Answer: Suppression of the rodent population could cause a trophic cascade
affecting native predators and prey
While off-target effects (A) are a technical concern, the most significant ecological risk
is the disruption of the food web (C), as the rodents may be a key prey or predator.
Horizontal gene transfer to non-target species (B) is extremely unlikely in animals.
Immune responses (D) affect efficiency but not ecological risk.
2. In synthetic biology, a minimal genome is defined as the set of genes essential for
survival under defined conditions. Which experimental approach is most
appropriate to identify such a set in a bacterium?
Answer: Systematic single-gene knockout using transposon mutagenesis and
viability screening
Systematic knockout (A) directly tests essentiality by determining which genes are
required for viability. Comparative genomics (B) identifies conserved but not
necessarily essential genes. Metabolic reconstruction (C) and expression analysis (D) do
not test essentiality experimentally.
3. A study of the gut microbiome in a cohort of individuals with metabolic syndrome
finds that fecal microbiota transplantation from lean donors improves insulin
sensitivity. Which of the following mechanisms is LEAST likely to contribute to this
effect?
Answer: Direct colonization of host tissues by donor bacteria, replacing host cells
in the liver
Donor bacteria typically colonize the gut lumen, not host tissues (C), making this
unlikely. SCFA production (A), barrier integrity (B), and bile acid modulation (D) are
well-documented mechanisms by which the microbiome influences host metabolism.
Page 2
,4. In a mouse model, a maternal high-fat diet leads to increased body weight and
glucose intolerance in offspring, even when the offspring are fed a normal diet. This
effect is observed for two generations. Which epigenetic mechanism is most directly
supported by these observations?
Answer: Paramutation-like transgenerational inheritance involving small RNAs
that modify gene expression in subsequent generations
Transgenerational epigenetic inheritance (D) involves mechanisms like small RNAs that
can persist across generations. DNA methylation changes in the germline (A) are
typically reprogrammed. Histone modifications (B) are not stably inherited. MicroRNA
transfer via placenta (C) affects first generation but not necessarily second.
5. A patient presents with rapidly progressive dementia and myoclonus. Brain MRI
shows cortical ribboning and high signal in the basal ganglia. CSF analysis is
positive for 14-3-3 protein and real-time quaking-induced conversion (RT-QuIC)
assay is positive. Which of the following statements about the causative agent is
correct?
Answer: It consists solely of misfolded protein that propagates by converting
normal cellular protein
The presentation and tests are classic for prion disease (e.g., Creutzfeldt-Jakob disease),
caused by misfolded prion protein (PrPSc) that converts normal PrPC (B). Prions
contain no nucleic acid (C). They are not viruses (A) or bacteria (D).
6. In an experiment, researchers inject double-stranded RNA (dsRNA)
corresponding to a specific gene into the body cavity of a nematode. They observe a
reduction in the expression of that gene in the nematode's offspring. Which of the
following mechanisms BEST explains the transmission of this effect to the next
generation?
Answer: The dsRNA is replicated by RNA-dependent RNA polymerase and
transported to the germline via the circulatory system
In C. elegans, RNAi can be systemic and inherited due to amplification by
RNA-dependent RNA polymerase and transport to germline (A). Integration into the
genome (B) is not typical for RNAi. Interferon response (C) is not present in nematodes.
Passive dilution (D) would not explain inheritance.
Page 3
, 7. A bacterial population initially susceptible to an antibiotic is exposed to
subinhibitory concentrations. After several generations, resistance emerges.
Whole-genome sequencing reveals that the resistance genes are located on a plasmid
that is identical to one found in a different bacterial species in the same environment.
Which process most likely explains this observation?
Answer: Conjugation-mediated horizontal gene transfer from the other species
followed by selection
The presence of an identical plasmid in two species strongly suggests conjugation (A),
as plasmids are often transferred via conjugative pili. De novo mutation (B) would not
produce an identical plasmid. Transformation (C) and transduction (D) can transfer
DNA, but the plasmid identity and context make conjugation most likely.
8. A population of butterflies exhibits two color morphs: light and dark. Over 50
years, as industrial pollution darkens tree trunks, the dark morph becomes more
common. After pollution controls lighten the trees, the light morph increases again.
Which of the following best describes the evolutionary process at play?
Answer: Directional selection shifting the population mean in response to
environmental change
The shift from light to dark and back to light represents directional selection (B) as the
environment changes. Disruptive selection (A) would favor both extremes at once, not
sequentially. Stabilizing selection (C) would maintain an intermediate. Balancing
selection (D) would keep both morphs present.
9. An emerging virus is discovered in bats that can infect human cells in vitro but
does not cause disease in animal models. The virus has a single-stranded RNA
genome of positive sense. Which of the following is the most immediate concern
regarding its pandemic potential?
Answer: The virus may mutate to become highly pathogenic in humans
RNA viruses have high mutation rates, so the most immediate concern is that it could
acquire mutations that increase virulence (A). Integration into the human genome (B) is
typical of retroviruses, not positive-sense RNA viruses. Aerosol transmission (C) is
possible but not immediate. Arthropod vectors (D) are not typical for bat-borne viruses.
Page 4
Answers Already Graded A+ Premium Exam Tested And
Verified
Subject Area Contemporary Issues in Biology
Description This exam covers advanced topics in contemporary biology, including
CRISPR-Cas9 gene editing, synthetic biology, microbiome research, epigenetics,
prion biology, RNA interference, horizontal gene transfer, climate change impacts
on evolution, and emerging infectious diseases. It emphasizes conceptual
understanding, experimental design, and data interpretation at the level expected
of top-tier US university students.
Expected Grade A+
Total Questions 139
Duration 3 hours
Learning Outcomes 1. Critically evaluate the ethical and technical limitations of CRISPR-Cas9 gene
drives
2. Analyze the ecological and evolutionary consequences of horizontal gene
transfer in prokaryotes
3. Interpret epigenetic inheritance patterns and their implications for
transgenerational effects
4. Apply knowledge of prion propagation mechanisms to understand
neurodegenerative diseases
5. Design experiments to test hypotheses in synthetic biology and RNA
interference
6. Assess the impact of climate change on species adaptation and extinction risk
7. Evaluate strategies for emerging infectious disease surveillance and control
Accreditation This exam adheres to the rigorous standards of Ivy League and R1 research
universities, requiring deep reasoning and synthesis across multiple biological
disciplines.
Page 1
,1. A research team proposes using a CRISPR-Cas9 gene drive to suppress a
population of invasive rodents on an island. Which of the following is the most
significant ecological risk that must be evaluated before release?
Answer: Suppression of the rodent population could cause a trophic cascade
affecting native predators and prey
While off-target effects (A) are a technical concern, the most significant ecological risk
is the disruption of the food web (C), as the rodents may be a key prey or predator.
Horizontal gene transfer to non-target species (B) is extremely unlikely in animals.
Immune responses (D) affect efficiency but not ecological risk.
2. In synthetic biology, a minimal genome is defined as the set of genes essential for
survival under defined conditions. Which experimental approach is most
appropriate to identify such a set in a bacterium?
Answer: Systematic single-gene knockout using transposon mutagenesis and
viability screening
Systematic knockout (A) directly tests essentiality by determining which genes are
required for viability. Comparative genomics (B) identifies conserved but not
necessarily essential genes. Metabolic reconstruction (C) and expression analysis (D) do
not test essentiality experimentally.
3. A study of the gut microbiome in a cohort of individuals with metabolic syndrome
finds that fecal microbiota transplantation from lean donors improves insulin
sensitivity. Which of the following mechanisms is LEAST likely to contribute to this
effect?
Answer: Direct colonization of host tissues by donor bacteria, replacing host cells
in the liver
Donor bacteria typically colonize the gut lumen, not host tissues (C), making this
unlikely. SCFA production (A), barrier integrity (B), and bile acid modulation (D) are
well-documented mechanisms by which the microbiome influences host metabolism.
Page 2
,4. In a mouse model, a maternal high-fat diet leads to increased body weight and
glucose intolerance in offspring, even when the offspring are fed a normal diet. This
effect is observed for two generations. Which epigenetic mechanism is most directly
supported by these observations?
Answer: Paramutation-like transgenerational inheritance involving small RNAs
that modify gene expression in subsequent generations
Transgenerational epigenetic inheritance (D) involves mechanisms like small RNAs that
can persist across generations. DNA methylation changes in the germline (A) are
typically reprogrammed. Histone modifications (B) are not stably inherited. MicroRNA
transfer via placenta (C) affects first generation but not necessarily second.
5. A patient presents with rapidly progressive dementia and myoclonus. Brain MRI
shows cortical ribboning and high signal in the basal ganglia. CSF analysis is
positive for 14-3-3 protein and real-time quaking-induced conversion (RT-QuIC)
assay is positive. Which of the following statements about the causative agent is
correct?
Answer: It consists solely of misfolded protein that propagates by converting
normal cellular protein
The presentation and tests are classic for prion disease (e.g., Creutzfeldt-Jakob disease),
caused by misfolded prion protein (PrPSc) that converts normal PrPC (B). Prions
contain no nucleic acid (C). They are not viruses (A) or bacteria (D).
6. In an experiment, researchers inject double-stranded RNA (dsRNA)
corresponding to a specific gene into the body cavity of a nematode. They observe a
reduction in the expression of that gene in the nematode's offspring. Which of the
following mechanisms BEST explains the transmission of this effect to the next
generation?
Answer: The dsRNA is replicated by RNA-dependent RNA polymerase and
transported to the germline via the circulatory system
In C. elegans, RNAi can be systemic and inherited due to amplification by
RNA-dependent RNA polymerase and transport to germline (A). Integration into the
genome (B) is not typical for RNAi. Interferon response (C) is not present in nematodes.
Passive dilution (D) would not explain inheritance.
Page 3
, 7. A bacterial population initially susceptible to an antibiotic is exposed to
subinhibitory concentrations. After several generations, resistance emerges.
Whole-genome sequencing reveals that the resistance genes are located on a plasmid
that is identical to one found in a different bacterial species in the same environment.
Which process most likely explains this observation?
Answer: Conjugation-mediated horizontal gene transfer from the other species
followed by selection
The presence of an identical plasmid in two species strongly suggests conjugation (A),
as plasmids are often transferred via conjugative pili. De novo mutation (B) would not
produce an identical plasmid. Transformation (C) and transduction (D) can transfer
DNA, but the plasmid identity and context make conjugation most likely.
8. A population of butterflies exhibits two color morphs: light and dark. Over 50
years, as industrial pollution darkens tree trunks, the dark morph becomes more
common. After pollution controls lighten the trees, the light morph increases again.
Which of the following best describes the evolutionary process at play?
Answer: Directional selection shifting the population mean in response to
environmental change
The shift from light to dark and back to light represents directional selection (B) as the
environment changes. Disruptive selection (A) would favor both extremes at once, not
sequentially. Stabilizing selection (C) would maintain an intermediate. Balancing
selection (D) would keep both morphs present.
9. An emerging virus is discovered in bats that can infect human cells in vitro but
does not cause disease in animal models. The virus has a single-stranded RNA
genome of positive sense. Which of the following is the most immediate concern
regarding its pandemic potential?
Answer: The virus may mutate to become highly pathogenic in humans
RNA viruses have high mutation rates, so the most immediate concern is that it could
acquire mutations that increase virulence (A). Integration into the human genome (B) is
typical of retroviruses, not positive-sense RNA viruses. Aerosol transmission (C) is
possible but not immediate. Arthropod vectors (D) are not typical for bat-borne viruses.
Page 4
