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1、Chapter 2Genes and Genomesa.The size of the viruses genome of difference a.The size of the viruses genome of difference varies greatly;varies greatly;130-375 kb PoxvirusPoxvirusHepatitis B virus,HBV3.2 kb2.4 2.4 Viral genomeViral genomeDNA genome:DNA genome:Mostly doubleMostly double-stranded,circul
2、ar or stranded,circular or linearlinearb.b.The viral genome consists of DNA or RNA The viral genome consists of DNA or RNA；DoubleDouble-stranded stranded linear DNAlinear DNACircular singleCircular single-stranded DNAstranded DNACircular doubleCircular double-stranded DNAstranded DNAMostly singleMos
3、tly single-stranded,linearstranded,linearRNA genome:RNA genome:SingleSingle-stranded stranded linear RNAlinear RNADoubleDouble-stranded stranded linear RNAlinear RNAc c.Genes are continuous and intermittent Genes are continuous and intermittent；Viruses that infect eukaryotic cells,some Viruses that
4、infect eukaryotic cells,some genes have introns genes have introns；环状双链环状双链DNADNA5243 bp5243 bpOriOrisimian virus 40,SV40Small tSmall tantigenantigenBig TBig Tantigenantigend d.Some RNA virus genomes are composed of discrete RNA strands Some RNA virus genomes are composed of discrete RNA strands；Inf
5、luenza A virus,H1N1Hemagglutinin Hemagglutinin（H H）Neuraminidase Neuraminidase（N N）8 8-segment singlesegment single-stranded RNAstranded RNASingle strand negative strand RNA,segmentedSingle strand negative strand RNA,segmentedReovirusReovirusLinear doubleLinear double-stranded stranded RNA,segmented
6、RNA,segmented1111segment dsRNAsegment dsRNACoat proteinCoat proteinUnderwear shell Underwear shell proteinproteinSome RNA virus genomes are composed of continuous RNA Some RNA virus genomes are composed of continuous RNA strands strands；Single strand positive Single strand positive strand RNAstrand
7、RNANucleocapsid Nucleocapsid protein(N)protein(N)Membrane Membrane Protein(M)Protein(M)SARS coronavirusSARS coronavirus，Single strand positive strand RNASingle strand positive strand RNASpike protein(S)Spike protein(S)Viral RNA polymeraseViral RNA polymeraseEbola virusEbola virusSingle stranded nega
8、tive strand RNA Single stranded negative strand RNA，18959nt18959ntAdenovirusLinear doubleLinear double-stranded DNA encodes two major classes of proteinsstranded DNA encodes two major classes of proteins.E4E4E2BE2BE2AE2AE1AE1A E1BE1BE3E3L2L2L3L3L4L4L5L5L1L1e.Functional units or transcription units o
9、f the e.Functional units or transcription units of the viral genome can be transcribed together into viral genome can be transcribed together into polycistronic mRNA polycistronic mRNA；DNADNAphage phix 174Circular singleCircular single-stranded DNAstranded DNAThe overlapping nature of the viral geno
10、me allows the virus to use limited nucleic acids to store more genetic information,thereby improving its ability to adapt during evolution5386nt编码编码25002500个氨基酸个氨基酸5386ntCodeCode 2500 amino acid2500 amino acidf.Gf.Gene overlapene overlapHuman Human papillomaviruspapillomavirusg.g.Most of the viral g
11、enome is used to encode proteins Most of the viral genome is used to encode proteins；CircularCircular doubledouble strandedstranded DNADNACapsid proteinCapsid proteinDNA replicateDNA replicateMembrane signaling proteinMembrane signaling proteinAssembly and releaseAssembly and releaseUpstream regulat
12、ory Upstream regulatory region(URR)region(URR)dsDNAHepatitis B virus,HBVHBcAgPolymeraseHBsAgHBcAgHepatitis B virus genomeHepatitis B virus genomeHepatitis B virus,HBV3182bpOpenOpen-loop partially doubleloop partially double-stranded DNAstranded DNAHepatitis B virus genomeHepatitis B virus genomercDN
13、ATraTranslnslateateProteinProteinmRNATranscrTranscriptioniption-ssDNAReverse Reverse TranscriTranscriptionption+ssDNAReplicateReplicateviralviralpaticlepaticlercDNAcccDNARepairRepairpgRNAVirus Virus particlesparticlesHuman immunodeficiency virus,HIVSingle strand positive strand RNASingle strand posi
14、tive strand RNAReverse transcriptaseReverse transcriptaseCore proteinCore proteinMembrane ProteinMembrane Protein（Diploid Diploid）Retrovirus genomeRetrovirus genomeHuman immunodeficiency virus,HIV+ssRNATransTranslatelateProteinProteinVirus Virus partiparticlesclesmRNATransTranscriptcriptionionssDNAR
15、everse Reverse TranscriTranscriptionption(+ssRNA)dsDNAIntegrIntegrationationThe summary of the structural characteristics of The summary of the structural characteristics of the viral genome is as follows the viral genome is as follows：The viral genome can be composed of DNA or RNA The viral genome
16、can be composed of DNA or RNA；Gene overlap Gene overlap；The functional units or transcription units of the The functional units or transcription units of the viral genome can be transcribed together into viral genome can be transcribed together into polycistronic mRNA polycistronic mRNA；Most of the
17、viral genome is used to encode proteins Most of the viral genome is used to encode proteins；Genes are continuous and intermittent Genes are continuous and intermittent；Some RNA virus genomes are composed of discrete RNA Some RNA virus genomes are composed of discrete RNA strands strands；The genome size of different viruses varies greatly The genome size of different viruses varies greatly；Thank You