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What is unique about the initiation of RNA synthesis in poliovirus replication?
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It uses a protein-linked primer, vpg, for RNA replication, rather than free nucleotides.
How does the nucleocapsid protein influence RNA synthesis in negative-strand RNA viruses like VSV?
It controls the switch from mRNA synthesis to replication of the viral genome.
What was Wendell Stanley's contribution to virology in 1935?
He crystallized the tobacco mosaic virus and initially believed that protein was its genetic material.
How do coronaviruses synthesize nested subgenomic RNAs?
Through discontinuous transcription leading to the creation of a set of RNA molecules with common 5' leader sequences.
Which experiment showed that DNA is the genetic material of viruses?
The Hershey Chase experiment in 1952.
How does reovirus maintain the integrity of its double-stranded RNA genome?
The genome never leaves the core of the virus particle; mRNAs are synthesized within this compartment to avoid exposure to the host's RNases.
What is the significance of two-metal ion catalysis in RNA polymerases?
This mechanism is crucial for the catalytic activity of polymerases, facilitating the polymerization of RNA.
Why does recombination occur in RNA viruses, and how is it regulated?
Recombination occurs through template switching by polymerase, and it's regulated by specific amino acids in the polymerase.
What is the primary reason for high mutation rates in RNA viruses?
RNA viruses have a lack of error correction mechanisms, leading to frequent incorporation of errors during replication.
What is the Gly-asp-asp (GDD) motif associated with?
It is a signature motif for RNA polymerases, essential for their catalytic function.
What are the four types of viral RNA mentioned in the notes?
Double-stranded RNA, single-stranded negative-sense RNA, single-stranded positive-sense RNA, and retroviruses with DNA intermediates.
Why don't plus-strand RNA viruses carry RNA polymerase in the viral particle?
Plus-strand RNA viruses do not need the polymerase in the particle as the plus-strand RNA can directly function as mRNA upon entering the host cell.
Describe the polymerase stuttering phenomenon.
It is a non-templated RNA synthesis mechanism where the polymerase 'stutters', adding extra nucleotides, leading to insertion mutations.
How was the viral origin of RNA synthesis demonstrated in the poliovirus experiment?
By using radioactive triphosphates to track RNA synthesis and finding that it was of viral, not cellular, origin.
What is the role of RdRP (RNA-dependent RNA polymerase) in the replication of negative-strand RNA viruses?
It is essential for the replication of negative and double-strand RNAs, as these viral RNAs cannot serve directly as mRNA.
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