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中南大学生物化学考研课件ch12核酸结构structureofnucleicacids06.ppt

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Chapter12ContentsThethreelevelsofDNAstructure（DNA的三级结构）TheprimarystructureofDNA（DNA一级结构）DNAsequencing（DNA测序）PrincipleofChainterminationmethodorSangerdideoxymethod链终止法或Sanger双脱氧方法原理ReviewonthestructuresofATP,dATP,ddATPDNAsequencing（DNA测序） ChainterminationmethodMethodologyofChainterminationmethodorSangerdideoxymethod链终止法或Sanger双脱氧方法的方法论ChainterminationmethodI---autoradiography放射自显影法SequencingnucleicacidsNotethat TheDNAfragmenttobe determinedshouldbein therange200~400bp IftheDNAfragment islongerthan400bp,it needstobecut(excised) intoseveralsmaller fragments.ChainterminationmethodII----autosequencing自动测序原理Automated DNAsequencing (自动DNA测序)SchematicdiagramofautomatedsequencingofDNA 自动测序的图解Examplesofgels测序胶示例BasicknowledgeaboutDNAsecondarystructuresB-DNA---standardDNAThedoublechainsinthehelixareantiparallelComparisoninstructuralfeaturesamongA,B,ZconformationformsofDNA(DNAA,B,Z三种构象形式的结构特征比较)A-DNARihgt-handed 11bp/pitch Pitchlength 2.46nm Lessoccurring,butmaybeinDNA:RNAhybridsB-DNAChangefromright-handedtoleft-handedCruciform十字形DNAcanbedenaturedbyheat(DNA可热变性） Meltingcurve溶解曲线 Meltingpointdependson(G+C)%andionicstrength熔点与GC含量和离子强度有关 IncreaseinmeltingpointwithriseofGC% Increaseinmeltingpointwithincreaseofionicstrength熔点随离子强度增加而增加 Denaturationbyheatmayberenaturatedbyslowlycoolingagain热变性后的DNA可通过缓慢冷却而复性Meltingcurve溶解曲线 IncreaseinMPwithriseofGC%Increaseinmeltingpointwithincreaseofionicstrength熔点随离子强度增加而增加DenaturationandrenaturationofDNADNAorganizationinchromosomes染色体中的DNA构架LocationofDNA Prokaryotes原核生物:innucleoid类核 Eukaryotes真核生物:chromosome染色体 Chromosome Definition：ComplexofnuclearDNAandhistoneproteins是核DNA和组蛋白的复合物 Histonesareverybasicproteins组蛋白是非常碱性的蛋白质 Contains~25%lysineorarginine含约25%的赖氨酸和精氨酸 EachchoromosomecontainsasinglelineardoublestrandedDNAmolecule. ThelengthofthepackagedDNAmoleculevaries Fromspeciestospecies,andamongthesamespecie FromonemitoticphasetoanothermitoticphaseComparisoninstructuralfeaturesofDNAbetweenprokaryotesandeucaryotes原核生物和真核生物染色体DNA结构特征比较Commontypeso