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1、ViralGenomeandStructuresLaboratoryofMedicalMolecularVirologyChangLiuhttp://v.163.com/special/opencourse/virology.htmlBreakthroughin1950’sTheviralnucleicacidgenomecarriestheinformationneededtoreplicate,build,andspreadvirionsintheworld.OneofthebuildingblocksofMolecularBi
2、ologyT4,TMVHershey-ChoseexperimentwithphageT4Fraenkel-Conrat’sworkwithTMVSevenGenomeTypesEitherDNAorRNAStructurallydiverse:linear,circular,segmented,gapped,single-stranded(+)strand,single-stranded(-)strand,singlestranded(ambisense),double-stranded,somehavecovalentlyatt
3、achedproteins,somehavecross-linkedendsofdouble-strandedDNARNAWorldhypothesisWhatinformationisencodedinaviralgenome?ReplicationofviralgenomeAssemblyandpackagingofthegenomeRegulationandtimingofthereplicationcycleModulationofhostdefensesSpreadtoothercellsandhostsInformati
4、onNotcontainedinviralgenomesNogenesencodingthecompleteproteinsynthesismachineryNogenesencodingproteininvolvedinenergyproductionormembranebiosynthesisNoclassicalcentromeresortelomeresfoundinstandardhostchromosomesTheBaltimoreSystemViralgenomemustmakemRNAthatcanbereadbyh
5、ostribosomesNOTall(+)RNAismRNAEachwayhasuniquepolymerase,primer,templateandterminationrequirementsEachvirusfamilyhasitsowncharacteristicgenomestrategySevenclassesdistinguishedbygenomereplicationstrategiesdsDNA,ssDNAdsRNA,+ssRNA,-ssRNA,RetrodsDNAgenomesTheproblemofrepli
6、catingtheendsoflinearDNAmoleculesthroughtheuseofRNAprimers.CirculardsDNAgenomesthatarereplicatedinthenucleusLineardsDNAgenomesthatarereplicatedinthenucleusLineardsDNAgenomesthatarereplicatedinthenucleusdsDNAgenomesthatarereplicatedinthecytoplasmssDNAgenomesAbasicproble
7、mwithassDNAgenome:RNAcanonlybemadefromadsDNAtemplate,ssDNAmustbeconvertedintodsDNAbeforemRNAismadeDNAsynthesismustprecedemRNAproductionLinearssDNAgenomesthatarereplicatedinthenucleusRNAgenomesCellshaveNORNA-dependentRNApolymerases(RdRp)toreplicatethegenomesofRNAviruses
8、,ortomakemRNAfromRNARNAvirusgenomesencodenovelRdRpPolymerasesproducebothRNAgenomesandmRNAfromRNAtemplates+ssRNA,-ssRN