, CONTEXT
Chapter 1 Virology: From Contagium Fluidum to Virome
Chapter 2 Principles of Virology
Chapter 3 Principles of Virus Structure
Chapter 4 Virus Entry and Uncoating
Chapter 5 Viral Replication Strategies
Chapter 6 Virus Assembly and Maturation
Chapter 7 Metabolism and Viral Infection
Chapter 8 Pathogenesis of Viral Infection
Chapter 9 Innate Immunity to Viruses
Chapter 10 The Adaptive Immune Response to Viruses
Chapter 11 Tumor Virology
Chapter 12 Evolution of Viral Proteins
Chapter 13 Epidemiology
Chapter 14 Antiviral Agents
Chapter 15 Immunization Against Viral Diseases
Chapter 16 Diagnostic Virology
Chapter 17 Giant Viruses
Chapter 18 Plant Viruses
Chapter 19 Insect Viruses
Chapter 20 Viruses and Prions of Yeasts, Fungi, and Protists
Chapter 21 Bacteriophages
Chapter 22 Prions
,Chapter 1: Virology
Q1. In the late 19th century, Ivanovsky and Beijerinck independently studied tobacco
mosaic disease. Which key experimental observation led Beijerinck to coin the term
contagium fluidum?
A. The infectious agent could be cultured on artificial media
B. The agent passed through porcelain filters that retained bacteria
C. The disease was caused by a toxin secreted by bacteria
D. The agent could be visualized under a light microscope
Answer: B
Rationale: Beijerinck observed that the infectious agent remained active after passing
through filters that trapped bacteria, concluding it was a new type of "fluid" pathogen—
contagium fluidum.
Keywords: contagium fluidum, filterable agent, tobacco mosaic virus, virus discovery
Q2. Which technological advancement allowed for the direct visualization of viruses for
the first time in the 1930s?
A. Fluorescence microscopy
B. Light microscopy with phase contrast
C. Electron microscopy
D. Confocal microscopy
Answer: C
Rationale: Electron microscopy enabled visualization of viral particles due to their small
size (20–300 nm), which is below the resolution limit of light microscopy.
Keywords: electron microscopy, virus visualization, nanoscale, viral morphology
Q3. The term virome refers to:
A. The total DNA content of a host organism
B. The collection of viral sequences found in a host or environment
C. Only the pathogenic viruses causing disease in humans
D. Viral proteins expressed during acute infection
,Answer: B
Rationale: The virome encompasses all viruses, including those infecting humans,
animals, plants, and bacteria, whether pathogenic or commensal.
Keywords: virome, viral diversity, metagenomics, host–virus interactions
Q4. Filtration experiments in early virology primarily distinguished viruses from:
A. Fungi
B. Protozoa
C. Bacteria
D. Prions
Answer: C
Rationale: Early filters retained bacteria but allowed viral particles to pass through,
differentiating viruses from bacterial pathogens.
Keywords: filterable agents, bacterial exclusion, virus size, early virology
Q5. The human virome is composed of:
A. Only DNA viruses
B. Only RNA viruses
C. DNA, RNA, and retroviruses, both latent and active
D. Only viruses that cause clinical disease
Answer: C
Rationale: Human virome studies show a mix of DNA, RNA, and retroviruses, many of
which persist asymptomatically or in latent form.
Keywords: human virome, latent viruses, retroviruses, viral diversity
Q6. Modern genomics has revealed that the virome plays an essential role in:
A. Only causing acute infections
B. Modulating host immunity and microbiome interactions
C. Replacing bacterial microbiota
D. Acting solely as a pathogen reservoir
Answer: B
Rationale: Metagenomic analyses indicate that commensal and persistent viruses
,influence host immunity, microbial ecology, and disease susceptibility.
Keywords: virome function, host–microbe interactions, genomics, immunomodulation
Q7. Dimitri Ivanovsky’s 1892 study of tobacco mosaic disease demonstrated:
A. The infectious agent was too small to be seen under a light microscope
B. Bacteria were responsible for the disease
C. Viruses required an electron microscope to detect
D. The agent could be neutralized by antibiotics
Answer: A
Rationale: Ivanovsky filtered sap through porcelain and noted that the filtrate remained
infectious, suggesting an ultra-small agent beyond light microscope detection.
Keywords: Ivanovsky, tobacco mosaic virus, filterable agent, virus size
Q8. Which of the following statements best describes the ecological significance of the
virome?
A. Viruses are purely pathogenic and harmful to ecosystems
B. Viruses are key regulators of microbial populations and nutrient cycling
C. Viruses are irrelevant outside human hosts
D. Viruses only affect laboratory cell cultures
Answer: B
Rationale: Environmental viromes regulate microbial populations, influence evolution
through horizontal gene transfer, and impact global nutrient cycles.
Keywords: virome ecology, viral role, microbial regulation, environmental virology
Q9. Beijerinck’s concept of a contagium vivum fluidum implied that viruses:
A. Could replicate independently outside host cells
B. Were obligate intracellular parasites
C. Could be easily cultured in nutrient agar
D. Were inert toxins
Answer: B
Rationale: Beijerinck inferred that the filterable agent was not a free-living organism but
,required host cells to replicate.
Keywords: obligate intracellular, viral replication, contagium fluidum, early virology
Q10. Which approach allowed scientists to study the diversity of viruses in the human
gut without culturing them?
A. Classical plaque assays
B. PCR and metagenomic sequencing
C. Hemagglutination assays
D. Electron microscopy only
Answer: B
Rationale: Metagenomics and high-throughput sequencing enable the detection and
characterization of viruses directly from biological samples without in vitro culture.
Keywords: metagenomics, human gut virome, unculturable viruses, sequencing
Q11. Which historical observation suggested that some viruses could establish
persistent infections?
A. Filterable agents caused immediate cell lysis
B. Some diseases recurred or remained asymptomatic after initial exposure
C. Viruses were visible under light microscopy
D. Viral genomes were always integrated into host DNA
Answer: B
Rationale: Clinical observations of recurrent infections (e.g., herpesviruses) hinted at
latency and viral persistence.
Keywords: persistent infection, latency, recurrent disease, herpesvirus
Q12. Which factor complicates the study of the human virome compared to bacterial
microbiome studies?
A. Viruses lack nucleic acids
B. Many viruses cannot be cultured in standard laboratory media
C. Viruses are too large for sequencing
D. The immune system eliminates all viruses immediately
,Answer: B
Rationale: A major challenge is that many viruses cannot be cultured, necessitating
sequence-based approaches to detect them.
Keywords: unculturable viruses, metagenomics, virome analysis, detection challenges
Q13. The diversity of viruses in the environment primarily results from:
A. Horizontal gene transfer, mutation, and recombination
B. Lack of host species
C. Stability of viral genomes over time
D. Exclusive replication in humans
Answer: A
Rationale: Mutation, recombination, and horizontal gene transfer drive viral diversity in
ecosystems.
Keywords: viral evolution, mutation, recombination, environmental virology
Q14. Which statement reflects the relationship between viruses and hosts as
understood from virome studies?
A. All viruses cause disease in their hosts
B. Many viruses coexist asymptomatically and may influence host physiology
C. Viral-host interactions are negligible for human health
D. Host genomes are unaffected by viral sequences
Answer: B
Rationale: Virome research shows many viruses are commensal or latent, impacting
immunity, gene regulation, and microbiome balance.
Keywords: host-virus interaction, commensal viruses, virome, human microbiome
Q15. The concept of filterable agents was critical in differentiating viruses from:
A. Prions and viroids
B. Fungi
C. Bacteria based on size exclusion
D. Protozoa
, Answer: C
Rationale: The filtration experiments indicated viruses were smaller than bacteria and
could pass through pores that trapped bacterial cells.
Keywords: filterable agent, virus discovery, Ivanovsky, Beijerinck
Q16. Modern viral metagenomics has revealed that most human-associated viruses:
A. Are highly pathogenic
B. Are bacteriophages or otherwise asymptomatic
C. Only infect epithelial cells
D. Cannot replicate in vivo
Answer: B
Rationale: Studies show the majority of human-associated viruses are bacteriophages
or viruses that do not cause overt disease.
Keywords: bacteriophages, commensal viruses, human virome, asymptomatic
Q17. Which early 20th-century experiment first demonstrated that a virus could infect
animals but not be seen under a light microscope?
A. Poliovirus injection into monkeys by Landsteiner and Popper
B. Influenza virus culture in eggs
C. Measles virus isolation in tissue culture
D. Tobacco mosaic virus filtration
Answer: A
Rationale: Landsteiner and Popper showed poliovirus caused disease in monkeys even
though it was invisible under light microscopy, confirming filterable pathogens in
animals.
Keywords: poliovirus, filterable agent, animal model, virus discovery
Q18. The human virome is influenced by all of the following EXCEPT:
A. Diet and microbiome composition
B. Age and immune status
C. Environmental exposures
D. Universal eradication of bacteriophages
Chapter 1 Virology: From Contagium Fluidum to Virome
Chapter 2 Principles of Virology
Chapter 3 Principles of Virus Structure
Chapter 4 Virus Entry and Uncoating
Chapter 5 Viral Replication Strategies
Chapter 6 Virus Assembly and Maturation
Chapter 7 Metabolism and Viral Infection
Chapter 8 Pathogenesis of Viral Infection
Chapter 9 Innate Immunity to Viruses
Chapter 10 The Adaptive Immune Response to Viruses
Chapter 11 Tumor Virology
Chapter 12 Evolution of Viral Proteins
Chapter 13 Epidemiology
Chapter 14 Antiviral Agents
Chapter 15 Immunization Against Viral Diseases
Chapter 16 Diagnostic Virology
Chapter 17 Giant Viruses
Chapter 18 Plant Viruses
Chapter 19 Insect Viruses
Chapter 20 Viruses and Prions of Yeasts, Fungi, and Protists
Chapter 21 Bacteriophages
Chapter 22 Prions
,Chapter 1: Virology
Q1. In the late 19th century, Ivanovsky and Beijerinck independently studied tobacco
mosaic disease. Which key experimental observation led Beijerinck to coin the term
contagium fluidum?
A. The infectious agent could be cultured on artificial media
B. The agent passed through porcelain filters that retained bacteria
C. The disease was caused by a toxin secreted by bacteria
D. The agent could be visualized under a light microscope
Answer: B
Rationale: Beijerinck observed that the infectious agent remained active after passing
through filters that trapped bacteria, concluding it was a new type of "fluid" pathogen—
contagium fluidum.
Keywords: contagium fluidum, filterable agent, tobacco mosaic virus, virus discovery
Q2. Which technological advancement allowed for the direct visualization of viruses for
the first time in the 1930s?
A. Fluorescence microscopy
B. Light microscopy with phase contrast
C. Electron microscopy
D. Confocal microscopy
Answer: C
Rationale: Electron microscopy enabled visualization of viral particles due to their small
size (20–300 nm), which is below the resolution limit of light microscopy.
Keywords: electron microscopy, virus visualization, nanoscale, viral morphology
Q3. The term virome refers to:
A. The total DNA content of a host organism
B. The collection of viral sequences found in a host or environment
C. Only the pathogenic viruses causing disease in humans
D. Viral proteins expressed during acute infection
,Answer: B
Rationale: The virome encompasses all viruses, including those infecting humans,
animals, plants, and bacteria, whether pathogenic or commensal.
Keywords: virome, viral diversity, metagenomics, host–virus interactions
Q4. Filtration experiments in early virology primarily distinguished viruses from:
A. Fungi
B. Protozoa
C. Bacteria
D. Prions
Answer: C
Rationale: Early filters retained bacteria but allowed viral particles to pass through,
differentiating viruses from bacterial pathogens.
Keywords: filterable agents, bacterial exclusion, virus size, early virology
Q5. The human virome is composed of:
A. Only DNA viruses
B. Only RNA viruses
C. DNA, RNA, and retroviruses, both latent and active
D. Only viruses that cause clinical disease
Answer: C
Rationale: Human virome studies show a mix of DNA, RNA, and retroviruses, many of
which persist asymptomatically or in latent form.
Keywords: human virome, latent viruses, retroviruses, viral diversity
Q6. Modern genomics has revealed that the virome plays an essential role in:
A. Only causing acute infections
B. Modulating host immunity and microbiome interactions
C. Replacing bacterial microbiota
D. Acting solely as a pathogen reservoir
Answer: B
Rationale: Metagenomic analyses indicate that commensal and persistent viruses
,influence host immunity, microbial ecology, and disease susceptibility.
Keywords: virome function, host–microbe interactions, genomics, immunomodulation
Q7. Dimitri Ivanovsky’s 1892 study of tobacco mosaic disease demonstrated:
A. The infectious agent was too small to be seen under a light microscope
B. Bacteria were responsible for the disease
C. Viruses required an electron microscope to detect
D. The agent could be neutralized by antibiotics
Answer: A
Rationale: Ivanovsky filtered sap through porcelain and noted that the filtrate remained
infectious, suggesting an ultra-small agent beyond light microscope detection.
Keywords: Ivanovsky, tobacco mosaic virus, filterable agent, virus size
Q8. Which of the following statements best describes the ecological significance of the
virome?
A. Viruses are purely pathogenic and harmful to ecosystems
B. Viruses are key regulators of microbial populations and nutrient cycling
C. Viruses are irrelevant outside human hosts
D. Viruses only affect laboratory cell cultures
Answer: B
Rationale: Environmental viromes regulate microbial populations, influence evolution
through horizontal gene transfer, and impact global nutrient cycles.
Keywords: virome ecology, viral role, microbial regulation, environmental virology
Q9. Beijerinck’s concept of a contagium vivum fluidum implied that viruses:
A. Could replicate independently outside host cells
B. Were obligate intracellular parasites
C. Could be easily cultured in nutrient agar
D. Were inert toxins
Answer: B
Rationale: Beijerinck inferred that the filterable agent was not a free-living organism but
,required host cells to replicate.
Keywords: obligate intracellular, viral replication, contagium fluidum, early virology
Q10. Which approach allowed scientists to study the diversity of viruses in the human
gut without culturing them?
A. Classical plaque assays
B. PCR and metagenomic sequencing
C. Hemagglutination assays
D. Electron microscopy only
Answer: B
Rationale: Metagenomics and high-throughput sequencing enable the detection and
characterization of viruses directly from biological samples without in vitro culture.
Keywords: metagenomics, human gut virome, unculturable viruses, sequencing
Q11. Which historical observation suggested that some viruses could establish
persistent infections?
A. Filterable agents caused immediate cell lysis
B. Some diseases recurred or remained asymptomatic after initial exposure
C. Viruses were visible under light microscopy
D. Viral genomes were always integrated into host DNA
Answer: B
Rationale: Clinical observations of recurrent infections (e.g., herpesviruses) hinted at
latency and viral persistence.
Keywords: persistent infection, latency, recurrent disease, herpesvirus
Q12. Which factor complicates the study of the human virome compared to bacterial
microbiome studies?
A. Viruses lack nucleic acids
B. Many viruses cannot be cultured in standard laboratory media
C. Viruses are too large for sequencing
D. The immune system eliminates all viruses immediately
,Answer: B
Rationale: A major challenge is that many viruses cannot be cultured, necessitating
sequence-based approaches to detect them.
Keywords: unculturable viruses, metagenomics, virome analysis, detection challenges
Q13. The diversity of viruses in the environment primarily results from:
A. Horizontal gene transfer, mutation, and recombination
B. Lack of host species
C. Stability of viral genomes over time
D. Exclusive replication in humans
Answer: A
Rationale: Mutation, recombination, and horizontal gene transfer drive viral diversity in
ecosystems.
Keywords: viral evolution, mutation, recombination, environmental virology
Q14. Which statement reflects the relationship between viruses and hosts as
understood from virome studies?
A. All viruses cause disease in their hosts
B. Many viruses coexist asymptomatically and may influence host physiology
C. Viral-host interactions are negligible for human health
D. Host genomes are unaffected by viral sequences
Answer: B
Rationale: Virome research shows many viruses are commensal or latent, impacting
immunity, gene regulation, and microbiome balance.
Keywords: host-virus interaction, commensal viruses, virome, human microbiome
Q15. The concept of filterable agents was critical in differentiating viruses from:
A. Prions and viroids
B. Fungi
C. Bacteria based on size exclusion
D. Protozoa
, Answer: C
Rationale: The filtration experiments indicated viruses were smaller than bacteria and
could pass through pores that trapped bacterial cells.
Keywords: filterable agent, virus discovery, Ivanovsky, Beijerinck
Q16. Modern viral metagenomics has revealed that most human-associated viruses:
A. Are highly pathogenic
B. Are bacteriophages or otherwise asymptomatic
C. Only infect epithelial cells
D. Cannot replicate in vivo
Answer: B
Rationale: Studies show the majority of human-associated viruses are bacteriophages
or viruses that do not cause overt disease.
Keywords: bacteriophages, commensal viruses, human virome, asymptomatic
Q17. Which early 20th-century experiment first demonstrated that a virus could infect
animals but not be seen under a light microscope?
A. Poliovirus injection into monkeys by Landsteiner and Popper
B. Influenza virus culture in eggs
C. Measles virus isolation in tissue culture
D. Tobacco mosaic virus filtration
Answer: A
Rationale: Landsteiner and Popper showed poliovirus caused disease in monkeys even
though it was invisible under light microscopy, confirming filterable pathogens in
animals.
Keywords: poliovirus, filterable agent, animal model, virus discovery
Q18. The human virome is influenced by all of the following EXCEPT:
A. Diet and microbiome composition
B. Age and immune status
C. Environmental exposures
D. Universal eradication of bacteriophages
