BIOD 171 Microbiology Module 6 – Latest Updated 2025–2026 |
Virology, Viral Replication, Diseases & Vaccines
1. Which answer best identifies or explains a virus?
A. a bacterial endospore
B. an acellular infectious agent containing nucleic acid within a protein capsid and sometimes an
envelope
C. a prokaryotic cell with independent metabolism
D. a eukaryotic parasite with ribosomes
Answer: B. an acellular infectious agent containing nucleic acid within a protein capsid and
sometimes an envelope
Rationale: Viruses are not cellular and depend on host cells for replication.
2. Which answer best identifies or explains a virion?
A. a host antibody
B. a fungal spore only
C. a complete infectious virus particle outside a host cell
D. a bacterial colony
Answer: C. a complete infectious virus particle outside a host cell
Rationale: A virion is the assembled extracellular form capable of initiating infection.
3. Which answer best identifies or explains a viral capsid?
A. the host cell membrane only
B. a ribosome-containing organelle
C. the protein shell surrounding the viral genome
D. a bacterial cell wall
Answer: C. the protein shell surrounding the viral genome
Rationale: Capsids protect viral nucleic acid and often participate in attachment or entry.
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,4. Which answer best identifies or explains a viral envelope?
A. a bacterial capsule
B. a peptidoglycan wall
C. a lipid membrane usually derived from host membranes and containing viral glycoproteins
D. a protein shell present in every virus
Answer: C. a lipid membrane usually derived from host membranes and containing viral
glycoproteins
Rationale: Enveloped viruses acquire host-derived lipid membranes containing viral proteins important
for attachment and entry.
5. Which answer best identifies or explains the viral genome?
A. always double-stranded DNA
B. peptidoglycan
C. always single-stranded RNA
D. DNA or RNA, but not both as the genome of a typical virion
Answer: D. DNA or RNA, but not both as the genome of a typical virion
Rationale: Viruses use either DNA or RNA as their genetic material, with diverse genome architectures.
6. Which answer best identifies or explains viral host range?
A. the spectrum of host species and cell types a virus can infect
B. the number of capsid proteins only
C. the diameter of a bacterial colony
D. the temperature at which a virus is stained
Answer: A. the spectrum of host species and cell types a virus can infect
Rationale: Host range depends strongly on receptor compatibility and intracellular factors.
7. Which answer best identifies or explains viral tropism?
A. preference for particular host tissues or cell types
B. bacterial motility
C. the ability to form endospores
D. viral resistance to staining
Answer: A. preference for particular host tissues or cell types
Rationale: Tropism reflects receptor expression and intracellular permissiveness in specific tissues.
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, 8. Which answer best identifies or explains the first step of many viral replication cycles?
A. Gram staining
B. attachment to a specific receptor on a susceptible host cell
C. sporulation
D. binary fission
Answer: B. attachment to a specific receptor on a susceptible host cell
Rationale: Specific viral proteins bind host receptors and determine susceptibility and tropism.
9. Which answer best identifies or explains viral penetration?
A. assembly of the capsid outside the host
B. formation of peptidoglycan
C. entry of the virion or its genome into the host cell
D. bacterial conjugation
Answer: C. entry of the virion or its genome into the host cell
Rationale: After attachment, viruses enter by fusion, endocytosis, or genome injection depending on
virus type.
10. Which answer best identifies or explains viral uncoating?
A. formation of bacterial endospores
B. Gram decolorization
C. host-cell cytokinesis
D. removal or disassembly of the capsid to release the viral genome
Answer: D. removal or disassembly of the capsid to release the viral genome
Rationale: Uncoating makes the viral genome accessible for transcription or replication.
11. Which answer best identifies or explains viral biosynthesis?
A. host antibody maturation only
B. bacterial binary fission
C. formation of agar colonies
D. production of viral nucleic acid and proteins using host and/or viral enzymes
Answer: D. production of viral nucleic acid and proteins using host and/or viral enzymes
Rationale: Viruses redirect cellular machinery and use viral enzymes where needed to synthesize
genomes and proteins.
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Virology, Viral Replication, Diseases & Vaccines
1. Which answer best identifies or explains a virus?
A. a bacterial endospore
B. an acellular infectious agent containing nucleic acid within a protein capsid and sometimes an
envelope
C. a prokaryotic cell with independent metabolism
D. a eukaryotic parasite with ribosomes
Answer: B. an acellular infectious agent containing nucleic acid within a protein capsid and
sometimes an envelope
Rationale: Viruses are not cellular and depend on host cells for replication.
2. Which answer best identifies or explains a virion?
A. a host antibody
B. a fungal spore only
C. a complete infectious virus particle outside a host cell
D. a bacterial colony
Answer: C. a complete infectious virus particle outside a host cell
Rationale: A virion is the assembled extracellular form capable of initiating infection.
3. Which answer best identifies or explains a viral capsid?
A. the host cell membrane only
B. a ribosome-containing organelle
C. the protein shell surrounding the viral genome
D. a bacterial cell wall
Answer: C. the protein shell surrounding the viral genome
Rationale: Capsids protect viral nucleic acid and often participate in attachment or entry.
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,4. Which answer best identifies or explains a viral envelope?
A. a bacterial capsule
B. a peptidoglycan wall
C. a lipid membrane usually derived from host membranes and containing viral glycoproteins
D. a protein shell present in every virus
Answer: C. a lipid membrane usually derived from host membranes and containing viral
glycoproteins
Rationale: Enveloped viruses acquire host-derived lipid membranes containing viral proteins important
for attachment and entry.
5. Which answer best identifies or explains the viral genome?
A. always double-stranded DNA
B. peptidoglycan
C. always single-stranded RNA
D. DNA or RNA, but not both as the genome of a typical virion
Answer: D. DNA or RNA, but not both as the genome of a typical virion
Rationale: Viruses use either DNA or RNA as their genetic material, with diverse genome architectures.
6. Which answer best identifies or explains viral host range?
A. the spectrum of host species and cell types a virus can infect
B. the number of capsid proteins only
C. the diameter of a bacterial colony
D. the temperature at which a virus is stained
Answer: A. the spectrum of host species and cell types a virus can infect
Rationale: Host range depends strongly on receptor compatibility and intracellular factors.
7. Which answer best identifies or explains viral tropism?
A. preference for particular host tissues or cell types
B. bacterial motility
C. the ability to form endospores
D. viral resistance to staining
Answer: A. preference for particular host tissues or cell types
Rationale: Tropism reflects receptor expression and intracellular permissiveness in specific tissues.
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, 8. Which answer best identifies or explains the first step of many viral replication cycles?
A. Gram staining
B. attachment to a specific receptor on a susceptible host cell
C. sporulation
D. binary fission
Answer: B. attachment to a specific receptor on a susceptible host cell
Rationale: Specific viral proteins bind host receptors and determine susceptibility and tropism.
9. Which answer best identifies or explains viral penetration?
A. assembly of the capsid outside the host
B. formation of peptidoglycan
C. entry of the virion or its genome into the host cell
D. bacterial conjugation
Answer: C. entry of the virion or its genome into the host cell
Rationale: After attachment, viruses enter by fusion, endocytosis, or genome injection depending on
virus type.
10. Which answer best identifies or explains viral uncoating?
A. formation of bacterial endospores
B. Gram decolorization
C. host-cell cytokinesis
D. removal or disassembly of the capsid to release the viral genome
Answer: D. removal or disassembly of the capsid to release the viral genome
Rationale: Uncoating makes the viral genome accessible for transcription or replication.
11. Which answer best identifies or explains viral biosynthesis?
A. host antibody maturation only
B. bacterial binary fission
C. formation of agar colonies
D. production of viral nucleic acid and proteins using host and/or viral enzymes
Answer: D. production of viral nucleic acid and proteins using host and/or viral enzymes
Rationale: Viruses redirect cellular machinery and use viral enzymes where needed to synthesize
genomes and proteins.
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