,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 – From Contagium Fluidum
to Virome
1. In the late 19th century, Dmitri Ivanovsky and Martinus Beijerinck
demonstrated that the causative agent of tobacco mosaic disease could pass
through filters that trapped bacteria. Beijerinck termed this agent a “contagium
fluidum.” What does this term imply about the nature of viruses?
A. Viruses are independent cellular organisms
B. Viruses are small, filterable infectious agents
C. Viruses reproduce by binary fission
D. Viruses are a type of bacterial toxin
Answer: B
Rationale: The term “contagium fluidum” was used to describe infectious
agents that were smaller than bacteria and could pass through porcelain
filters, indicating a non-cellular, filterable nature. This foundational work led to
the concept of viruses as unique pathogens.
Key words: Contagium fluidum, filterable agents, tobacco mosaic virus, virus
discovery
2. Early virologists relied on host plants or animals to propagate viruses.
Which of the following experimental systems was first successfully used to
demonstrate viral replication?
A. Bacterial culture media
B. Insect cell lines
C. Tobacco plants
D. Yeast culture
Answer: C
Rationale: Tobacco plants were the first experimental host system used by
Ivanovsky and Beijerinck to study the replication of tobacco mosaic virus,
illustrating the requirement of living cells for viral propagation.
Key words: Experimental systems, tobacco mosaic virus, host requirement
,3. Which statement best describes the human virome?
A. Only pathogenic viruses are part of the human virome
B. The human virome includes all viruses that infect humans, including
commensals and latent viruses
C. The human virome consists exclusively of bacteriophages
D. The human virome is static and does not change over time
Answer: B
Rationale: The human virome encompasses all viruses associated with
humans, including asymptomatic, commensal, and latent infections. It is
dynamic and influenced by age, environment, and health status.
Key words: Human virome, latent viruses, commensal viruses, viral diversity
4. Advances in genomics have transformed virology by allowing:
A. Culture of all viruses in standard bacterial media
B. Visualization of viral particles using light microscopy
C. Identification and classification of viruses without cultivation
D. Complete elimination of viral disease
Answer: C
Rationale: Genomics and metagenomics allow detection, sequencing, and
classification of viruses directly from samples without the need for culture,
revolutionizing virology and the study of the virome.
Key words: Genomics, metagenomics, virus discovery, uncultivable viruses
5. Which of the following is considered a filterable agent, as first described in
classical virology experiments?
A. Escherichia coli
B. Influenza virus
C. Streptococcus pneumoniae
D. Bacillus subtilis
Answer: B
Rationale: Influenza virus, like tobacco mosaic virus, is a classic example of a
filterable agent, capable of passing through bacterial filters, distinguishing
viruses from bacteria.
Key words: Filterable agent, influenza, virus identification
6. The concept of the “virome” emphasizes that:
A. All viruses are harmful pathogens
,B. Viruses are integral components of host biology and ecology
C. Viruses only infect humans
D. Viruses exist solely in laboratory conditions
Answer: B
Rationale: The virome concept highlights that viruses are not just pathogens
but also integral to host physiology, microbial ecology, and evolutionary
processes.
Key words: Virome, host ecology, virus diversity
7. Which early experimental finding distinguished viruses from bacteria?
A. Ability to grow on nutrient agar
B. Size larger than bacterial cells
C. Inability to replicate outside living cells
D. Production of ATP independently
Answer: C
Rationale: Viruses are obligate intracellular parasites; unlike bacteria, they
cannot replicate independently outside living cells, which was a key feature
identified in early virology.
Key words: Obligate intracellular, virus vs bacteria, replication
8. The term “virology” was coined to describe:
A. The study of viral evolution exclusively
B. The scientific discipline focused on viruses and virus-host interactions
C. Bacterial toxins that mimic viruses
D. Viral cultivation in cell-free media
Answer: B
Rationale: Virology is the study of viruses, their replication, structure,
pathogenesis, host interactions, and role in ecology and evolution.
Key words: Virology definition, virus-host interaction, scientific discipline
9. Which of the following viruses was among the first to be studied due to its
ability to cause visible symptoms in plants?
A. Influenza virus
B. Tobacco mosaic virus
C. Herpes simplex virus
D. Poliovirus
,Answer: B
Rationale: Tobacco mosaic virus was studied early because it produced clear
lesions in tobacco plants, allowing observation of viral replication and
transmission.
Key words: Tobacco mosaic virus, plant virus, early virology
10. Which factor contributed most to the realization that viruses could not be
observed by light microscopy in early studies?
A. Their intracellular replication
B. Their filterability
C. Their small size below the resolution of light microscopes
D. Their ability to form plaques on agar
Answer: C
Rationale: Viruses are smaller than the resolution limit of light microscopes
(~200 nm), necessitating electron microscopy for direct visualization.
Key words: Virus size, microscopy, electron microscopy
11. Which of the following best explains why some viruses remain undetected
in traditional culture-based virology?
A. They are too large to enter cells
B. They cannot replicate in standard culture systems
C. They always cause visible cytopathic effects
D. They produce abundant metabolic byproducts
Answer: B
Rationale: Many viruses require specific hosts or conditions for replication and
may not produce cytopathic effects, making them invisible to classical culture-
based methods.
Key words: Unculturable viruses, host specificity, cytopathic effect
12. In modern virology, metagenomic sequencing of environmental samples
primarily allows:
A. Direct cultivation of viral particles
B. Detection of viral sequences without prior knowledge of the virus
C. Isolation of viral proteins only
D. Visualization of viral capsids
Answer: B
Rationale: Metagenomic sequencing identifies viral genetic material directly
,from samples, enabling discovery of novel viruses without needing prior
isolation or cultivation.
Key words: Metagenomics, viral discovery, sequencing
13. Which of the following statements about the virome in humans is TRUE?
A. All viruses present cause disease
B. Most viruses are commensal or latent
C. Bacteriophages are absent in the human virome
D. The virome composition is identical in all individuals
Answer: B
Rationale: Many viruses in humans are latent or commensal, playing roles in
microbiome dynamics and immune system modulation.
Key words: Human virome, latent virus, commensal virus
14. Beijerinck’s concept of “contagium vivum fluidum” was instrumental in
understanding:
A. Virus-mediated metabolic pathways
B. Viruses as infectious, non-cellular entities
C. Viral oncogenesis
D. Viral immunology
Answer: B
Rationale: Beijerinck recognized that viruses were infectious but non-cellular
agents, distinct from bacteria, laying the foundation for virology.
Key words: Beijerinck, contagious fluid, non-cellular pathogen
15. Which technological advance most dramatically expanded the known
diversity of viruses in the environment?
A. Light microscopy
B. Agar culture
C. Next-generation sequencing
D. Gram staining
Answer: C
Rationale: Next-generation sequencing (NGS) allows large-scale detection of
viral genomes in environmental and clinical samples, vastly expanding the
catalog of viruses.
Key words: NGS, environmental virome, viral diversity
, 16. Which historical observation first suggested that an infectious agent could
be smaller than bacteria?
A. Observation of plaques on agar
B. Filtered sap from infected plants could transmit disease
C. Cultivation in bacterial broth
D. Visualization under the light microscope
Answer: B
Rationale: The key experiment was that filtered sap from infected plants (free
of bacteria) could still transmit disease, indicating a sub-bacterial infectious
agent.
Key words: Filtered sap, sub-bacterial agent, tobacco mosaic virus
17. The study of the human virome is particularly important because:
A. All viruses are immediately pathogenic
B. Viruses influence host immunity and microbiome dynamics
C. Viruses only infect immune cells
D. It eliminates the need for vaccines
Answer: B
Rationale: The human virome affects immunity, microbial ecology, and host
health, including both beneficial and pathogenic effects.
Key words: Virome, immunity, microbiome interaction
18. Which characteristic is shared by all viruses identified by early virologists?
A. Contain ribosomes for protein synthesis
B. Replicate only within living host cells
C. Capable of independent metabolism
D. Visible under a standard light microscope
Answer: B
Rationale: Obligate intracellular replication is a universal property of viruses,
distinguishing them from other microorganisms.
Key words: Obligate intracellular, universal virus property, replication
19. Which of the following best exemplifies a “virome-associated” ecological
effect?
A. Viruses causing acute hepatitis in humans
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 – From Contagium Fluidum
to Virome
1. In the late 19th century, Dmitri Ivanovsky and Martinus Beijerinck
demonstrated that the causative agent of tobacco mosaic disease could pass
through filters that trapped bacteria. Beijerinck termed this agent a “contagium
fluidum.” What does this term imply about the nature of viruses?
A. Viruses are independent cellular organisms
B. Viruses are small, filterable infectious agents
C. Viruses reproduce by binary fission
D. Viruses are a type of bacterial toxin
Answer: B
Rationale: The term “contagium fluidum” was used to describe infectious
agents that were smaller than bacteria and could pass through porcelain
filters, indicating a non-cellular, filterable nature. This foundational work led to
the concept of viruses as unique pathogens.
Key words: Contagium fluidum, filterable agents, tobacco mosaic virus, virus
discovery
2. Early virologists relied on host plants or animals to propagate viruses.
Which of the following experimental systems was first successfully used to
demonstrate viral replication?
A. Bacterial culture media
B. Insect cell lines
C. Tobacco plants
D. Yeast culture
Answer: C
Rationale: Tobacco plants were the first experimental host system used by
Ivanovsky and Beijerinck to study the replication of tobacco mosaic virus,
illustrating the requirement of living cells for viral propagation.
Key words: Experimental systems, tobacco mosaic virus, host requirement
,3. Which statement best describes the human virome?
A. Only pathogenic viruses are part of the human virome
B. The human virome includes all viruses that infect humans, including
commensals and latent viruses
C. The human virome consists exclusively of bacteriophages
D. The human virome is static and does not change over time
Answer: B
Rationale: The human virome encompasses all viruses associated with
humans, including asymptomatic, commensal, and latent infections. It is
dynamic and influenced by age, environment, and health status.
Key words: Human virome, latent viruses, commensal viruses, viral diversity
4. Advances in genomics have transformed virology by allowing:
A. Culture of all viruses in standard bacterial media
B. Visualization of viral particles using light microscopy
C. Identification and classification of viruses without cultivation
D. Complete elimination of viral disease
Answer: C
Rationale: Genomics and metagenomics allow detection, sequencing, and
classification of viruses directly from samples without the need for culture,
revolutionizing virology and the study of the virome.
Key words: Genomics, metagenomics, virus discovery, uncultivable viruses
5. Which of the following is considered a filterable agent, as first described in
classical virology experiments?
A. Escherichia coli
B. Influenza virus
C. Streptococcus pneumoniae
D. Bacillus subtilis
Answer: B
Rationale: Influenza virus, like tobacco mosaic virus, is a classic example of a
filterable agent, capable of passing through bacterial filters, distinguishing
viruses from bacteria.
Key words: Filterable agent, influenza, virus identification
6. The concept of the “virome” emphasizes that:
A. All viruses are harmful pathogens
,B. Viruses are integral components of host biology and ecology
C. Viruses only infect humans
D. Viruses exist solely in laboratory conditions
Answer: B
Rationale: The virome concept highlights that viruses are not just pathogens
but also integral to host physiology, microbial ecology, and evolutionary
processes.
Key words: Virome, host ecology, virus diversity
7. Which early experimental finding distinguished viruses from bacteria?
A. Ability to grow on nutrient agar
B. Size larger than bacterial cells
C. Inability to replicate outside living cells
D. Production of ATP independently
Answer: C
Rationale: Viruses are obligate intracellular parasites; unlike bacteria, they
cannot replicate independently outside living cells, which was a key feature
identified in early virology.
Key words: Obligate intracellular, virus vs bacteria, replication
8. The term “virology” was coined to describe:
A. The study of viral evolution exclusively
B. The scientific discipline focused on viruses and virus-host interactions
C. Bacterial toxins that mimic viruses
D. Viral cultivation in cell-free media
Answer: B
Rationale: Virology is the study of viruses, their replication, structure,
pathogenesis, host interactions, and role in ecology and evolution.
Key words: Virology definition, virus-host interaction, scientific discipline
9. Which of the following viruses was among the first to be studied due to its
ability to cause visible symptoms in plants?
A. Influenza virus
B. Tobacco mosaic virus
C. Herpes simplex virus
D. Poliovirus
,Answer: B
Rationale: Tobacco mosaic virus was studied early because it produced clear
lesions in tobacco plants, allowing observation of viral replication and
transmission.
Key words: Tobacco mosaic virus, plant virus, early virology
10. Which factor contributed most to the realization that viruses could not be
observed by light microscopy in early studies?
A. Their intracellular replication
B. Their filterability
C. Their small size below the resolution of light microscopes
D. Their ability to form plaques on agar
Answer: C
Rationale: Viruses are smaller than the resolution limit of light microscopes
(~200 nm), necessitating electron microscopy for direct visualization.
Key words: Virus size, microscopy, electron microscopy
11. Which of the following best explains why some viruses remain undetected
in traditional culture-based virology?
A. They are too large to enter cells
B. They cannot replicate in standard culture systems
C. They always cause visible cytopathic effects
D. They produce abundant metabolic byproducts
Answer: B
Rationale: Many viruses require specific hosts or conditions for replication and
may not produce cytopathic effects, making them invisible to classical culture-
based methods.
Key words: Unculturable viruses, host specificity, cytopathic effect
12. In modern virology, metagenomic sequencing of environmental samples
primarily allows:
A. Direct cultivation of viral particles
B. Detection of viral sequences without prior knowledge of the virus
C. Isolation of viral proteins only
D. Visualization of viral capsids
Answer: B
Rationale: Metagenomic sequencing identifies viral genetic material directly
,from samples, enabling discovery of novel viruses without needing prior
isolation or cultivation.
Key words: Metagenomics, viral discovery, sequencing
13. Which of the following statements about the virome in humans is TRUE?
A. All viruses present cause disease
B. Most viruses are commensal or latent
C. Bacteriophages are absent in the human virome
D. The virome composition is identical in all individuals
Answer: B
Rationale: Many viruses in humans are latent or commensal, playing roles in
microbiome dynamics and immune system modulation.
Key words: Human virome, latent virus, commensal virus
14. Beijerinck’s concept of “contagium vivum fluidum” was instrumental in
understanding:
A. Virus-mediated metabolic pathways
B. Viruses as infectious, non-cellular entities
C. Viral oncogenesis
D. Viral immunology
Answer: B
Rationale: Beijerinck recognized that viruses were infectious but non-cellular
agents, distinct from bacteria, laying the foundation for virology.
Key words: Beijerinck, contagious fluid, non-cellular pathogen
15. Which technological advance most dramatically expanded the known
diversity of viruses in the environment?
A. Light microscopy
B. Agar culture
C. Next-generation sequencing
D. Gram staining
Answer: C
Rationale: Next-generation sequencing (NGS) allows large-scale detection of
viral genomes in environmental and clinical samples, vastly expanding the
catalog of viruses.
Key words: NGS, environmental virome, viral diversity
, 16. Which historical observation first suggested that an infectious agent could
be smaller than bacteria?
A. Observation of plaques on agar
B. Filtered sap from infected plants could transmit disease
C. Cultivation in bacterial broth
D. Visualization under the light microscope
Answer: B
Rationale: The key experiment was that filtered sap from infected plants (free
of bacteria) could still transmit disease, indicating a sub-bacterial infectious
agent.
Key words: Filtered sap, sub-bacterial agent, tobacco mosaic virus
17. The study of the human virome is particularly important because:
A. All viruses are immediately pathogenic
B. Viruses influence host immunity and microbiome dynamics
C. Viruses only infect immune cells
D. It eliminates the need for vaccines
Answer: B
Rationale: The human virome affects immunity, microbial ecology, and host
health, including both beneficial and pathogenic effects.
Key words: Virome, immunity, microbiome interaction
18. Which characteristic is shared by all viruses identified by early virologists?
A. Contain ribosomes for protein synthesis
B. Replicate only within living host cells
C. Capable of independent metabolism
D. Visible under a standard light microscope
Answer: B
Rationale: Obligate intracellular replication is a universal property of viruses,
distinguishing them from other microorganisms.
Key words: Obligate intracellular, universal virus property, replication
19. Which of the following best exemplifies a “virome-associated” ecological
effect?
A. Viruses causing acute hepatitis in humans
