Replication of viruses MCQs With Answer

Introduction: Replication of viruses MCQs With Answer provides B. Pharm students a focused, exam-oriented review of viral replication strategies, mechanisms, and antiviral targets. This concise guide covers key concepts such as attachment, penetration, uncoating, genome replication in DNA and RNA viruses, reverse transcription, segmentation, recombination, replication compartments, and host–virus interactions. It emphasizes clinically relevant details like viral polymerases, error rates, assembly, release, and common antiviral drug targets, helping students link molecular mechanisms to therapeutic approaches. Perfect for revision, test preparation, and building strong pharmacology foundations. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the first step in the virus replication cycle?

• Attachment
• Genome replication
• Assembly
• Release

Correct Answer: Attachment

Q2. Which mechanism do many enveloped viruses use to enter host cells?

• Endocytosis followed by membrane fusion
• Direct nuclear import
• Spontaneous genome diffusion
• Mitochondrial translocation

Correct Answer: Endocytosis followed by membrane fusion

Q3. What is the primary purpose of viral uncoating?

• To release the viral genome into the host cell
• To assemble new virions
• To form viral envelopes
• To trigger apoptosis

Correct Answer: To release the viral genome into the host cell

Q4. Where do most DNA viruses replicate their genomes?

• Host cell nucleus
• Host cell mitochondria
• Host cell Golgi apparatus
• Host cell lysosomes

Correct Answer: Host cell nucleus

Q5. Which family of DNA viruses uniquely replicates entirely in the cytoplasm?

• Poxviridae
• Adenoviridae
• Herpesviridae
• Polyomaviridae

Correct Answer: Poxviridae

Q6. RNA viruses require which enzyme to synthesize RNA from an RNA template?

• RNA-dependent RNA polymerase (RdRp)
• Reverse transcriptase
• DNA polymerase I
• DNA-dependent RNA polymerase II

Correct Answer: RNA-dependent RNA polymerase (RdRp)

Q7. What is a defining feature of positive-sense single-stranded RNA (+ssRNA) genomes?

• The genome can act directly as mRNA
• The genome must be transcribed to complementary RNA before translation
• The genome integrates into the host genome as DNA
• The genome is double-stranded in virions

Correct Answer: The genome can act directly as mRNA

Q8. Negative-sense single-stranded RNA (-ssRNA) viruses must carry which component in the virion?

• RNA-dependent RNA polymerase
• Host ribosomes
• Host DNA polymerase
• Reverse transcriptase

Correct Answer: RNA-dependent RNA polymerase

Q9. Which enzyme is essential for retroviral replication and synthesizes DNA from an RNA template?

• Reverse transcriptase
• RNA-dependent RNA polymerase
• DNA ligase
• Topoisomerase

Correct Answer: Reverse transcriptase

Q10. Which viral enzyme mediates integration of viral DNA into the host genome?

• Integrase
• Protease
• Helicase
• Polymerase sliding clamp

Correct Answer: Integrase

Q11. Cap-snatching, a mechanism to prime viral mRNA synthesis, is characteristic of which virus group?

• Orthomyxoviruses (e.g., influenza)
• Picornaviruses (e.g., poliovirus)
• Herpesviruses (e.g., HSV)
• Parvoviruses

Correct Answer: Orthomyxoviruses (e.g., influenza)

Q12. Reassortment of genome segments is most relevant to which type of virus?

• Segmented RNA viruses
• Single-segment DNA viruses
• Non-segmented positive-sense RNA viruses
• Tandem repeat DNA viruses

Correct Answer: Segmented RNA viruses

Q13. Which phenomenon best explains major sudden changes in influenza antigenicity (antigenic shift)?

• Reassortment of genome segments
• Point mutations in hemagglutinin
• Viral protease activity
• Host immune suppression

Correct Answer: Reassortment of genome segments

Q14. How do coronaviruses generate subgenomic mRNAs?

• Discontinuous transcription during negative-strand synthesis
• Cap-independent translation initiation only
• Host splicing of viral DNA
• Proteolytic cleavage of a polyprotein into mRNAs

Correct Answer: Discontinuous transcription during negative-strand synthesis

Q15. Which viral RNA element allows internal initiation of translation, often used by picornaviruses?

• Internal ribosome entry site (IRES)
• Poly(A) tail
• Cap structure
• tRNA primer

Correct Answer: Internal ribosome entry site (IRES)

Q16. Programmed ribosomal frameshifting is exploited by many viruses to:

• Produce two proteins from overlapping ORFs such as Gag-Pol
• Initiate host DNA replication
• Cap viral mRNAs
• Signal viral envelope formation

Correct Answer: Produce two proteins from overlapping ORFs such as Gag-Pol

Q17. Viral proteases commonly function to:

• Process polyproteins into functional viral proteins
• Replicate viral genomes directly
• Integrate viral DNA into host chromosomes
• Form the viral capsid shell

Correct Answer: Process polyproteins into functional viral proteins

Q18. Enveloped viruses typically acquire their envelope by which process?

• Budding from host membranes
• Capsid dissolution in cytosol
• Direct secretion through nuclear pores
• Protein-assisted diffusion across membrane

Correct Answer: Budding from host membranes

Q19. Non-enveloped viruses are most commonly released from infected cells by:

• Host cell lysis
• Budding with envelope acquisition
• Exocytosis through Golgi only
• Direct passage through gap junctions

Correct Answer: Host cell lysis

Q20. What does a plaque assay measure?

• Infectious viral titer expressed as plaque-forming units (PFU)
• Total viral protein concentration
• Viral genome copy number by PCR
• Antibody neutralization only

Correct Answer: Infectious viral titer expressed as plaque-forming units (PFU)

Q21. What is the eclipse phase of viral infection?

• Interval when no infectious virions are detectable within cells after entry
• Period of peak extracellular virion release
• Time before viral attachment
• Duration of immune clearance

Correct Answer: Interval when no infectious virions are detectable within cells after entry

Q22. Multiplicity of infection (MOI) is defined as:

• The ratio of infectious particles to target cells
• The number of viral proteins produced per cell
• The time required for one replication cycle
• The percentage of cells lysed

Correct Answer: The ratio of infectious particles to target cells

Q23. The quasispecies concept in RNA viruses refers to:

• A cloud of genetically diverse but related genomes within a population
• A single clonal genome sequence in all virions
• Integration of viral DNA into the host genome
• Formation of defective interfering particles only

Correct Answer: A cloud of genetically diverse but related genomes within a population

Q24. High mutation rates in RNA viruses are largely due to:

• Lack of proofreading by RNA-dependent RNA polymerases
• High-fidelity host polymerases
• Viral error-correcting exonucleases
• Stable double-stranded genomes

Correct Answer: Lack of proofreading by RNA-dependent RNA polymerases

Q25. Small DNA viruses such as parvoviruses rely on which enzyme for genome replication?

• Host DNA-dependent DNA polymerase
• Viral RNA-dependent RNA polymerase
• Viral reverse transcriptase
• Viral DNA polymerase with proofreading

Correct Answer: Host DNA-dependent DNA polymerase

Q26. Viral tropism is primarily determined by:

• Presence of specific host cell receptors
• The viral genome length only
• The color of the host cell
• Host mitochondrial activity

Correct Answer: Presence of specific host cell receptors

Q27. What is the role of viral packaging signals?

• Ensure selective encapsidation of viral genomes
• Promote host cell apoptosis
• Mediate immune recognition
• Bind host ribosomes for translation

Correct Answer: Ensure selective encapsidation of viral genomes

Q28. During reverse transcription, which activity of reverse transcriptase removes the RNA strand of an RNA–DNA hybrid?

• RNase H activity
• Helicase activity
• Endonuclease V activity
• Topoisomerase activity

Correct Answer: RNase H activity

Q29. What term describes the integrated, replication-competent form of a retroviral genome in the host DNA?

• Provirus
• Plasmid
• Virion
• Epitope

Correct Answer: Provirus

Q30. Which process commonly occurs during maturation of many enveloped viruses?

• Proteolytic cleavage of structural polyproteins
• Immediate integration into host DNA
• Formation of double-stranded RNA genomes
• Removal of viral envelope

Correct Answer: Proteolytic cleavage of structural polyproteins

Q31. Where do many enveloped viruses bud to acquire their envelope?

• Plasma membrane or internal membranes like Golgi/ER
• Mitochondrial inner membrane exclusively
• From the nuclear lamina only
• Across the lysosomal membrane

Correct Answer: Plasma membrane or internal membranes like Golgi/ER

Q32. Which viral protein class often mediates early modulation of host cell processes after entry?

• Tegument or accessory proteins delivered with the virion
• Late structural capsid proteins only
• Host ribosomal proteins
• Membrane lipases

Correct Answer: Tegument or accessory proteins delivered with the virion

Q33. Satellite viruses require what to replicate?

• A helper virus that supplies replication functions
• Only host polymerases without any helper
• Integration into bacterial genomes
• Independent reverse transcriptase

Correct Answer: A helper virus that supplies replication functions

Q34. Which in vitro assay is commonly used to evaluate antiviral drug efficacy by measuring reduction in plaque numbers?

• Plaque reduction assay
• ELISA for antibodies only
• Western blot of viral proteins
• Gram staining

Correct Answer: Plaque reduction assay

Q35. What are viral replication factories or compartments?

• Localized cytoplasmic or nuclear sites concentrating viral replication machinery
• Host extracellular matrix deposits
• Irreversible aggregates of misfolded viral proteins
• Only membrane-bound autophagosomes

Correct Answer: Localized cytoplasmic or nuclear sites concentrating viral replication machinery

Q36. How do some picornaviruses shut off host cap-dependent translation?

• Cleavage of eukaryotic initiation factor eIF4G by viral protease
• Inhibition of host DNA replication forks
• Induction of mitochondrial biogenesis
• Blocking nuclear export of rRNA only

Correct Answer: Cleavage of eukaryotic initiation factor eIF4G by viral protease

Q37. Genetic recombination in viruses differs from reassortment because recombination:

• Exchanges nucleotide sequences within genomes rather than swapping segments
• Occurs only in segmented viruses
• Is the same as antigenic shift
• Involves host DNA incorporation only

Correct Answer: Exchanges nucleotide sequences within genomes rather than swapping segments

Q38. What is the principle behind lethal mutagenesis (error catastrophe) as an antiviral strategy?

• Increase viral mutation rate to exceed tolerable error threshold and collapse population
• Enhance viral polymerase fidelity to reduce diversity
• Block capsid assembly irreversibly
• Stimulate host immune hyperactivation only

Correct Answer: Increase viral mutation rate to exceed tolerable error threshold and collapse population

Q39. Which polymerase is inherently error-prone and contributes to retroviral diversity?

• Reverse transcriptase (RNA-dependent DNA polymerase)
• Host DNA polymerase delta
• Host RNA polymerase II
• DNA-dependent DNA polymerase I

Correct Answer: Reverse transcriptase (RNA-dependent DNA polymerase)

Q40. Single-stranded DNA (ssDNA) viruses must first convert their genome to which form before replication?

• Double-stranded DNA (dsDNA)
• Double-stranded RNA (dsRNA)
• Single-stranded RNA (ssRNA)
• Protein–DNA hybrids only

Correct Answer: Double-stranded DNA (dsDNA)

Q41. Which herpesvirus feature supports rapid initiation of productive infection?

• Tegument proteins delivered upon entry that modulate host transcription
• Immediate degradation of host DNA
• Insulation of genome in the cytoplasm only
• Exclusive use of host mitochondria for replication

Correct Answer: Tegument proteins delivered upon entry that modulate host transcription

Q42. Latency in herpesviruses is characterized by:

• Maintenance of viral genome as an episome with limited gene expression
• Continuous production of large numbers of extracellular virions
• Integration into bacterial genomes
• Permanent loss of all viral genes

Correct Answer: Maintenance of viral genome as an episome with limited gene expression

Q43. Which best distinguishes lytic from persistent viral infections?

• Lytic infections lead to cell death; persistent infections allow prolonged virus presence without immediate lysis
• Persistent infections always produce more virions per hour than lytic infections
• Lytic infections never elicit immune responses
• Persistent infections always integrate into host genome

Correct Answer: Lytic infections lead to cell death; persistent infections allow prolonged virus presence without immediate lysis

Q44. Capsid assembly in many viruses is driven primarily by:

• Self-assembly of capsid proteins guided by genome and packaging signals
• Host chaperone-mediated nuclear export only
• Direct ATP-driven motor proteins exclusively
• Mitochondrial insertion of capsid subunits

Correct Answer: Self-assembly of capsid proteins guided by genome and packaging signals

Q45. Viral helicases function to:

• Unwind nucleic acid secondary structures during replication
• Form the viral envelope bilayer
• Attach virions to host cell receptors
• Degrade host ribosomal RNA only

Correct Answer: Unwind nucleic acid secondary structures during replication

Q46. Viral origins of replication are recognized by:

• Viral and/or host replication proteins that assemble initiation complexes
• Only host ribosomes
• Host lysosomal enzymes exclusively
• Mitochondrial DNA polymerase gamma solely

Correct Answer: Viral and/or host replication proteins that assemble initiation complexes

Q47. Which class of antiviral drugs directly targets reverse transcriptase?

• Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)
• Neuraminidase inhibitors
• Protease inhibitors
• Fusion inhibitors only

Correct Answer: Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)

Q48. Protease inhibitors as antivirals primarily act by:

• Blocking cleavage of viral polyproteins required for maturation
• Inhibiting viral entry receptors directly
• Preventing viral genome integration
• Degrading host DNA

Correct Answer: Blocking cleavage of viral polyproteins required for maturation

Q49. RdRp-targeting antivirals (e.g., nucleotide analogs) primarily interfere with:

• Viral RNA synthesis by causing chain termination or error incorporation
• Capsid assembly via ionic disruption
• Viral budding from host membranes only
• Host mRNA splicing exclusively

Correct Answer: Viral RNA synthesis by causing chain termination or error incorporation

Q50. Vaccination prevents many viral infections primarily by:

• Inducing neutralizing antibodies that block attachment/entry
• Directly killing viruses in the bloodstream
• Blocking host DNA replication permanently
• Inhibiting host protein synthesis broadly

Correct Answer: Inducing neutralizing antibodies that block attachment/entry

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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