吉林大学遗传学第十章 遗传物质的分子基础

第十章遗传的分子基础ProofofDNAasGeneticMaterialTransformation转化inBacteria(FrederickGriffith.1928)CharacteristicsofS.pneumoniae肺炎(链)双球菌StrainsWhenGrownonBloodAgarMedium

ColonyMorphology菌落形态TypeAppearanceSizeCapsule荚膜Virulence毒性IIRRoughSmallAbsentAvirulentIISSmoothLargePresentVirulent

ColonyMorphologyTypeAppearanceSizeCapsuleVirulenceIIIRRoughSmallAbsentAvirulentIIISSmoothLargePresentVirulent

ReactionwithAntiserumPreparedAgainstTypeTypeIISTypeIIISIIRNoneNoneIISAgglutination凝集None

ReactionwithAntiserumPreparedAgainstTypeTypeIISTypeIIISIIIRNoneNoneIIISNoneAgglutinationDNA:theTransformationMaterial(OswaldAveryandhiscolleagues1944)TheanalyticaltoolsAveryetc.usedwerethefollowing:1.Ultra-centrifugation超速离心2.Electrophoresis电泳3.UltravioletAbsorption紫外吸收4.ElementaryChemicalAnalysis化学元素分析

TheHershey-ChaseExperimentProofofRNAasGeneticMaterialAvarietyofstrainsoftobaccomosaicvirustobaccomosaicvirus(TMV)exist.ManystrainscausedistinctivesymptomsonindicatorplantsTMVparticlescanbedissociatedinto解离RNAandproteincomponents.TheseparatedRNAandproteincanbemixedtogethertoreforminfectiousviralparticles.ExperimentswithtobaccovirusesrevealedthatRNA,aswellasDNA,couldcarryhereditaryinformation.

vulgaremaskedyellowribgrassnoneMixedparticles,withRNAofonestrainandproteinofanother,canalsobeformed.Mixedparticlesareinfectious.Notethesymptomstheyproduce(C).

CCoatProteinSource

vulgaramaskedyellowribgrass

vulgaramaskedyellowribgrass

RNAsource第二节核酸的化学组成及结构分析NucleicAcidChemistryJohannMisecher(1844–1895)“nuclein”.Ribonucleicacids(RNA)Deoxyribonucleicacids(DNA)核糖核苷酸12345脱氧核糖核苷酸核糖2’-脱氧核糖嘧啶环嘌呤环胞嘧啶尿嘧啶胸腺嘧啶鸟嘌呤腺嘌呤尿苷脱氧腺苷酸蛋白质生物合成脂质代谢能量代谢3’-5’磷酸二酯键DNAStructureErwinChargaffandChargaff’rulesA+G=T+CTheDoubleHelixWatsonandCrick(1953)X-raydiffractionphotographoftheBformofpurifiedDNAfibers.TheNobelPrizeinPhysiologyorMedicine1962DNA双链构象改变因素：1、核苷酸顺序2、碱基组成3、盐的种类4、相对湿度Tm(meltingtemperature解链温度)Thetemperatureatwhichapopulationofdouble-strandednucleicmoleculesishalf-dissociatedintosinglestrands.Thisistakentobethemeltingtemperatureforthatspeciesofnucleicacid.Denaturation变性andRenaturation复性DNA紫外吸收RNA脱氧核糖——核糖；T——U单链3.自身互补配对形成双链区。rRNA(ribosomalRNA)mRNA(messengerRNA)tRNA(transferRNA)snRNA(smallnuclearRNA)antisenseRNAtelomeraseRNAprimer(invivo)DNA的复制Replication(SemiconservativeReplication)半保留复制(SemidiscontinuousReplication)半不连续复制TheMeselson-StahlexperimentEnzymology酶学ofDNAReplicationHelicase解旋酶(StrandSeparation)SinglestrandDNA-bindingProteins单链DNA结合蛋白(SSBs)Primerase引物酶(primer)Ligase连接酶Telome