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Lecture 6

BIOL442 - Lecture 6 - (-) RNA.pdf

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BIOL 442
Christine Dupont

Set 6RNANegative strand RNA animal virusDescribe the morphology of this virusaIf the genome is in segments what family might it belong to Give an example of a virus from this familybPredict how it carries outcGenome replication tell me about the polymeraseTranscriptiontranslation what has to happen firstHow might it code for its proteins assume segmenteddWhat might be some advantages of having segmented genomeeDisadvantagesfSegmented and multipartite genomesAnimalstrand RNA viruses plants and some insect DNA virusesAdvantagesNucleic acids that are very long are more subject to physical damage especially when ss many small pieces is more stableFaster to replicateAllows for reassortment genetic variationDisadvantagesRNA more labile than DNA degrades very easilyWorse for ss vs ds genomesAssociation with nucleoprotein protectsSs genomes have no way to repair themselves no templateAll the segments must get made and packagedSegments Genome divided into 2 or more physically separate molecules of nucleic acidPackaged within same virion particleNoteHIV has two identical copies ofstrand genome but this is not the same as segmentedHow do segmented viruses ensure all segments are packaged togetherEg influenza virus OrthomyxoviridaeAll 8 segments are presentPackaging segmented genomesSome do this specifically Serial dependencePackaging of a specific designated segment occurs firstOnly when this occurs then next designated segment enters then next etcRatio of total virus particles infectious particles1OthersRely on odds of producing many particles A proportion will have the correct number of segmentsRatio of total virus particles infectious particleslargeIf multiple defective virions infect the same cell get complementation and productive infectionMultipartiteSeveral genomic segments but each is packaged into a separate virion particleCapsid is the same composition but may vary in size depending on how big packaged segment isFound in plants some insects eg PolydnaviridaeUp to 25 ds circular DNA molecules could be more than 1 per virionHave a problem in ensuring infection occurs with the collective genomeProbably why this format is limited to plants some insectsPlants use very efficient insect vectors for ensuring a good dose of particles are taken up and transferredInsect viruses eg polydnaviruses the virions are released in very high concentrations into the ovary and get injected along with the egg strand animal RNA virusesRhabdoviridae Orthomyxoviridae Paramyxoviridae Filoviridae Bunyaviridae ArenaviridaeObviously translation cannot occur directly fromstrand viruses genome is not infectiousNeeds viral RNAdependent RNA polymerase to first makestrand mRNA for translation New Section 1 Page 1
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