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11 Cards in this Set
- Front
- Back
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What are the three basic replication stategies of viruses?
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1.DNA-based
2.RNA-based 3.DNA based with reverse transcriptase |
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Relate (+) and (-) sense RNA to the orientation of mRNA.
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(+) sense RNA has the same polarity and orientation as mRNA, (-) sense RNA has the opposite polarity and orientation.
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For viruses that employ a DNA-based replication strategy, what polymerases are used for replication and transcription? Are they virally encoded or part of the host cell?
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*replication: DNA-dependent DNA pol
*transcription: DNA-dependent RNA pol *most often the virus uses hist cell enzymes |
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How are (+) sense ssRNA viruses...
*replicated? *transcribed? |
*Replication is via a virally-encoded RNA-dependent RNA pol...a (-) sense template is made first and then (+) sense strands polymerized
*because they are in the same orientation as mRNA these viruses are directly translated by host cell ribosomes without a separate transcription step |
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How are (-) sense ssRNA viruses...
*replicated? *transcribed? |
*a virally encoded RNA-dependent RNA pol is used for replication...this RNA pol is typically packaged inside the virion
*after the viral RNA-dependent RNA pol has synthesized (+) sense RNA, translation occurs via host cell ribosomes |
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How do dsRNA viruses replicate?
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Via a RNA-dependent RNA pol that is packaged inside the virion.
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What can be said about the nature of the viral genome and its tendency to gravitate to certain parts of the host cell?
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DNA viruses tend to move into the nucleus, while RNA viruses tend to stay in the cytoplasm.
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What is the reverse transcriptase enzyme?
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A virally encoded RNA-dependent DNA pol that is also able to degrade RNA that is in a hybrid complex with DNA and synthesize DNA in a DNA-dependent manner.
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What are the three reactions involved in reverse transcription?
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1.Synthesis of DNA alongside viral RNA to form a hybrid complex.
2.Selective degradation of viral RNA 3.Synthesis of a complementary strand of DNA to form a homogenous complex |
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T/F:
Net amplification occurs when RT synthesizes a complementary strand of DNA alongside the viral RNA. |
False: because the viral RNA strand will be degraded, there is no net amplification in this replication step. Once the DNA complex is complete, it is transcribed in a manner that does amplify the viral genome.
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What is the mutation rate for RT? What does this imply?
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*1 error per every 10^4 nucleotides
*this means there is a mutation for every genome transcribed, so even within a single patient no two viruses will be exactly the same (theoretically atleast) |
