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26 Cards in this Set
- Front
- Back
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What type of a virus is hepatitis A?
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Picornavirus
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What type of genetic material is in hepatitis A?
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+ strand Rna
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What type of a virus is hepatitis B?
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Hepadnavirus
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What type of genetic material is in hepatitis B?
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ds DNA
THE ONLY HEPATITIS VIRUS TO HAVE DNA! |
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What type of a virus is hepatitis C?
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Hepacivirus
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What is the type of genetic material in hepatitis C?
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+ strand RNA
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Where does RNA virus replication take place? What types of hepatitis viruses are RNA viruses?
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Inside the cytoplasm on intracellular membranes (think RER)
Hepatitis A, C |
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What are the four mechanisms for getting multiple proteins from one piece of RNA?
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Polyproteins
Subgenomic mRNAs RNA splicing Internal translation initiation (IRES) |
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How do cells get multiple proteins from one polyprotein mRNA?
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Cleavage via proteases
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What is unique about picornovirus (Hep A) mRNA?
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Has no cap --> different form of translation initiation
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What kind of mRNA expression system does Hepatitis use?
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Polyproteins
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What is the mechanism for the expression of multiple proteins from one mRNA molecule via subgenomic mRNAs?
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Skipping of the polymerase to different spots on the mRNA molecule within the cytoplasm
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What is the effect of PKR on protein synthesis?
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Shuts it down: phosphorylates eIF2 to inactivate it, a protein that is essential for cap-dependent protein synthesis
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What is the stimulus for PKR translation? Is the protein active all by its lonesome?
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Interferon signalling due to a viral infection
NO! The protein needs dsRNA to be activated |
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What is the molecule that activates PKR?
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dsRNA
Signal to shut down protein synthesis |
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What is the mechanism by which viruses get around the stoppage of cap-depended mRNA translation by PKR?
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Cap independent translation - finding creative ways to have the host machinery make the viral proteins without the need for a cap!
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What is unique about the genetic material of HBV?
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DNA
Partially closed - one strand is shorter than the other |
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What is the cause of HBV mRNA synthesis in the liver rather than somewhere else?
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Tissue-specific transcription factors
THESE SPECIFIC FACTORS ARE NEEDED ; GIVES SPECIFICITY TO THE LIVER |
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What enzyme does Hepatitis B encode? Why?
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Reverse transcriptase
It needs to remake its DNA genome from the pre-genomic RNA from the nucleus |
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Where is the location of genome synthesis within HBV?
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Inside the viral particle, within the nucleus
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What is a major cause of genetic diversity within viruses?
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Erroneous polymerases!
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What is the result of erroneous polymerase activity in viruses?
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Quasi-species formation - all of the viruses have some mutation in them to make them very different from each other.
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What is a defective virus?
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A virus that requires proteins from ANOTHER virus to be able to replicat
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What is an example of a defective virus?
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Hepatitis delta agent; requires HBV
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What is the one type of hepatitis virus that directly causes damage to hepatocytes?
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Hepatitis A
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What is the mechanism by which all three viruses cause damage to hepatocytes?
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Initiation of an immune response that damages the cells:
NK cells cytotoxic T cells |
