MIMG C185A Final Exam | Questions
and Answers | 2026 Revised Update |
100% Correct - UCLA
SECTION I: Viral Structure & Replication (12 Questions)
Q1: A virology student isolates a virus with a single-stranded DNA genome that
replicates via a rolling hairpin mechanism. According to Baltimore classification,
which group does this virus belong to?
A. Group I (dsDNA)
B. Group II (ssDNA)
C. Group IV ((+)ssRNA)
D. Group VII (dsDNA-RT)
Correct Answer: B
Rationale: Correct because Group II (ssDNA) viruses, exemplified by
parvoviruses, possess single-stranded DNA genomes that replicate via a rolling
hairpin intermediate. Per virology standard, Baltimore classification groups
viruses based on nucleic acid type and replication strategy.
Q2: During influenza A virus replication in the host cell cytoplasm, which
mechanism is used to generate capped 5' ends on viral mRNAs?
A. De novo capping by viral methyltransferase
B. Cap snatching from host pre-mRNAs
C. Internal ribosome entry site (IRES)-mediated translation
D. Polyadenylation signal recognition
Correct Answer: B
Rationale: Correct because influenza A virus, a (-)ssRNA virus with segmented
genome, utilizes cap snatching to steal 5' methylated caps from host pre-mRNAs
via the viral polymerase complex (PB1, PB2, PA). Pathogenesis mechanism
involves hijacking host transcription machinery for viral mRNA synthesis.
,Q3: Which viral replication step immediately follows uncoating of a herpes
simplex virus (HSV) virion entering a permissive epithelial cell?
A. Assembly of capsid proteins in the cytoplasm
B. Transport of capsid to nucleus and release of viral DNA
C. Budding through the nuclear envelope
D. Reverse transcription of viral genome
Correct Answer: B
Rationale: Correct because HSV, a Group I dsDNA virus, undergoes uncoating at
the nuclear pore, releasing the viral genome into the nucleus where transcription
and replication occur. Per virology standard, dsDNA viruses typically replicate in
the nucleus.
Q4: A newly discovered enveloped virus buds from the plasma membrane of
infected cells without causing cell lysis. Which of the following is most likely true
about its release mechanism?
A. It acquires its envelope from the nuclear membrane
B. It is a non-enveloped virus with icosahedral symmetry
C. It buds through the plasma membrane, acquiring a lipid envelope with viral
glycoproteins
D. It is released only upon host cell necrosis
Correct Answer: C
Rationale: Correct because enveloped viruses such as retroviruses and (-)ssRNA
viruses acquire their lipid bilayer envelope by budding through host cell
membranes, incorporating viral glycoproteins during the process. Pathogenesis
mechanism involves non-lytic release preserving host cell viability temporarily.
Q5: The RNA-dependent RNA polymerase (RdRp) of RNA viruses lacks
proofreading activity. What is the primary virological consequence of this
enzymatic property?
A. Increased fidelity of genome replication
, B. High mutation rates and rapid viral evolution
C. Enhanced integration into host chromosomes
D. Reduced need for host transcription factors
Correct Answer: B
Rationale: Correct because RdRp lacks 3'→5' exonuclease proofreading activity,
resulting in error-prone replication with mutation rates approximately 10^-4 per
nucleotide per replication cycle. Per virology standard, this drives antigenic drift
and facilitates immune evasion.
Q6: A picornavirus infects a host cell and initiates protein synthesis. Which
mechanism allows translation of its genomic RNA in the absence of a 5' cap
structure?
A. Cap snatching from host mRNAs
B. Internal ribosome entry site (IRES)-mediated cap-independent translation
C. Polyadenylation-dependent translation
D. Ribosomal shunting via viral protease cleavage
Correct Answer: B
Rationale: Correct because picornaviruses, as Group IV (+)ssRNA viruses,
possess an internal ribosome entry site (IRES) in their 5' untranslated region that
recruits ribosomes directly without a 5' cap. Pathogenesis mechanism involves
shutting down host cap-dependent translation while maintaining viral protein
synthesis.
Q7: Which of the following correctly pairs a Baltimore classification group with its
representative virus and replication strategy?
A. Group III: Influenza A virus — dsRNA genome replicates in cytoplasm
B. Group V: Rabies virus — (-)ssRNA genome, viral RdRp required for mRNA
synthesis
C. Group VI: Hepatitis B virus — (+)ssRNA genome with reverse transcription
D. Group VII: Human immunodeficiency virus — dsDNA genome with RNA
intermediate
and Answers | 2026 Revised Update |
100% Correct - UCLA
SECTION I: Viral Structure & Replication (12 Questions)
Q1: A virology student isolates a virus with a single-stranded DNA genome that
replicates via a rolling hairpin mechanism. According to Baltimore classification,
which group does this virus belong to?
A. Group I (dsDNA)
B. Group II (ssDNA)
C. Group IV ((+)ssRNA)
D. Group VII (dsDNA-RT)
Correct Answer: B
Rationale: Correct because Group II (ssDNA) viruses, exemplified by
parvoviruses, possess single-stranded DNA genomes that replicate via a rolling
hairpin intermediate. Per virology standard, Baltimore classification groups
viruses based on nucleic acid type and replication strategy.
Q2: During influenza A virus replication in the host cell cytoplasm, which
mechanism is used to generate capped 5' ends on viral mRNAs?
A. De novo capping by viral methyltransferase
B. Cap snatching from host pre-mRNAs
C. Internal ribosome entry site (IRES)-mediated translation
D. Polyadenylation signal recognition
Correct Answer: B
Rationale: Correct because influenza A virus, a (-)ssRNA virus with segmented
genome, utilizes cap snatching to steal 5' methylated caps from host pre-mRNAs
via the viral polymerase complex (PB1, PB2, PA). Pathogenesis mechanism
involves hijacking host transcription machinery for viral mRNA synthesis.
,Q3: Which viral replication step immediately follows uncoating of a herpes
simplex virus (HSV) virion entering a permissive epithelial cell?
A. Assembly of capsid proteins in the cytoplasm
B. Transport of capsid to nucleus and release of viral DNA
C. Budding through the nuclear envelope
D. Reverse transcription of viral genome
Correct Answer: B
Rationale: Correct because HSV, a Group I dsDNA virus, undergoes uncoating at
the nuclear pore, releasing the viral genome into the nucleus where transcription
and replication occur. Per virology standard, dsDNA viruses typically replicate in
the nucleus.
Q4: A newly discovered enveloped virus buds from the plasma membrane of
infected cells without causing cell lysis. Which of the following is most likely true
about its release mechanism?
A. It acquires its envelope from the nuclear membrane
B. It is a non-enveloped virus with icosahedral symmetry
C. It buds through the plasma membrane, acquiring a lipid envelope with viral
glycoproteins
D. It is released only upon host cell necrosis
Correct Answer: C
Rationale: Correct because enveloped viruses such as retroviruses and (-)ssRNA
viruses acquire their lipid bilayer envelope by budding through host cell
membranes, incorporating viral glycoproteins during the process. Pathogenesis
mechanism involves non-lytic release preserving host cell viability temporarily.
Q5: The RNA-dependent RNA polymerase (RdRp) of RNA viruses lacks
proofreading activity. What is the primary virological consequence of this
enzymatic property?
A. Increased fidelity of genome replication
, B. High mutation rates and rapid viral evolution
C. Enhanced integration into host chromosomes
D. Reduced need for host transcription factors
Correct Answer: B
Rationale: Correct because RdRp lacks 3'→5' exonuclease proofreading activity,
resulting in error-prone replication with mutation rates approximately 10^-4 per
nucleotide per replication cycle. Per virology standard, this drives antigenic drift
and facilitates immune evasion.
Q6: A picornavirus infects a host cell and initiates protein synthesis. Which
mechanism allows translation of its genomic RNA in the absence of a 5' cap
structure?
A. Cap snatching from host mRNAs
B. Internal ribosome entry site (IRES)-mediated cap-independent translation
C. Polyadenylation-dependent translation
D. Ribosomal shunting via viral protease cleavage
Correct Answer: B
Rationale: Correct because picornaviruses, as Group IV (+)ssRNA viruses,
possess an internal ribosome entry site (IRES) in their 5' untranslated region that
recruits ribosomes directly without a 5' cap. Pathogenesis mechanism involves
shutting down host cap-dependent translation while maintaining viral protein
synthesis.
Q7: Which of the following correctly pairs a Baltimore classification group with its
representative virus and replication strategy?
A. Group III: Influenza A virus — dsRNA genome replicates in cytoplasm
B. Group V: Rabies virus — (-)ssRNA genome, viral RdRp required for mRNA
synthesis
C. Group VI: Hepatitis B virus — (+)ssRNA genome with reverse transcription
D. Group VII: Human immunodeficiency virus — dsDNA genome with RNA
intermediate
