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Animal Viruses: RNA Virus Synthesis & Replication quiz

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  • What enzyme do RNA viruses use to replicate their genomes?
    RNA viruses use a replicase enzyme, which is an RNA-dependent RNA polymerase, to replicate their genomes.
  • Where does replication of most RNA viruses occur within the host cell?
    Most RNA viruses replicate in the cytoplasm of the host cell.
  • How is the genome of plus single-stranded RNA (ssRNA) viruses used upon entering the host cell?
    The genome of plus ssRNA viruses acts as mRNA and is directly translated by host ribosomes to produce viral proteins, including replicase.
  • What is the role of the replicase enzyme in plus ssRNA viruses?
    Replicase synthesizes a complementary minus ssRNA strand from the plus ssRNA, which is then used to make more plus ssRNA genomes.
  • Does the replicase enzyme enter the host cell with plus ssRNA viruses during initial infection?
    No, the replicase enzyme is not present during initial infection; it is produced after the plus ssRNA is translated inside the host cell.
  • Why can't minus single-stranded RNA (ssRNA) viruses use their genome directly for translation?
    Minus ssRNA cannot be directly translated because only plus ssRNA (mRNA) can be recognized by host ribosomes for protein synthesis.
  • What must minus ssRNA viruses bring with them into the host cell during infection?
    Minus ssRNA viruses must bring the replicase enzyme with them during initial infection to synthesize plus ssRNA (mRNA) from their genome.
  • How is the plus ssRNA produced in minus ssRNA virus infections used?
    The plus ssRNA can be translated to make viral proteins or used as a template by replicase to replicate the minus ssRNA genome.
  • Why is it important for minus ssRNA viruses to package replicase in new viral particles?
    Packaging replicase ensures it is present during the next infection, which is essential since minus ssRNA cannot be directly translated to make replicase.
  • What type of genome do double-stranded RNA (dsRNA) viruses have?
    Double-stranded RNA viruses have genomes consisting of both plus (coding) and minus (non-coding) RNA strands.
  • Can double-stranded RNA be directly translated by host ribosomes?
    No, dsRNA cannot be directly translated; it must first be used as a template to make plus ssRNA (mRNA).
  • What enzyme must enter the host cell with dsRNA viruses during infection?
    The replicase enzyme must enter with dsRNA viruses to synthesize plus ssRNA from the dsRNA genome.
  • What are the two main uses of plus ssRNA produced from dsRNA viruses?
    Plus ssRNA can be translated to make viral proteins or used as a template to replicate the original dsRNA genome.
  • Why must the replicase enzyme be packaged in new dsRNA viral particles?
    Replicase must be packaged to ensure it is present during the next infection, as dsRNA cannot be directly translated to produce replicase.
  • What is the main function of the replicase enzyme in RNA virus replication?
    The replicase enzyme synthesizes new RNA molecules from an RNA template, enabling the replication of viral RNA genomes.