大学分子生物学经典双语课件C2 gene and chromosome.ppt

Chapter2GeneandChromosome,Contents,2.1StructureofDNA,Definition：thenucletideresiduesequenceofthepolynucleotidechain；Linkage：3,5-phosphodiesterbond；Backbone：phosphate+pentose；Direction：53；,-DNAdoublehelix,XrayphotographofDNAwithhighquality：DNAspecimensfromdifferentspecieshavethesameresults（constantwidth;3.4nm）；Chargaffrules：theruleofthecompositionofDNAPhysicalchemistrystudiesandacidandalkalititratestudiesonDNAbase；,Experimentalbasis,ThreedimensionalstructureofDNA,10.5bp/turn,Sugar-Pbackboneisperpendiculartotheplanarbasepairs,5,5,3,3,Pitchlength,TheWatson-CrickBformDNADeducedbymodelbuilding,11,20,Fig8-15,chargedPO4-ontheoutside,keynotesofDNAdoublehelix,TwopolynucleotidechainsinaDNAdoublehelix;Alongthesameaxis，twochainsarewoundaroundeachother,resultinginaright-handeddoublehelix;Formsamajorgrooveandaminorgroove,Thebaseslieontheinside，thesugar-phosphatebackboneisontheoutside;Thebasesareflatstructure,lyinginpairsperpendiculartotheaxis,Thediameterofthedoublehelixis2nm;Thereisacompleteturnevery3.4nm,with10bpperturn.,2.1.2.1Stablefactorsofthedoublehelix,Base-stackinginteraction（hydrophobiceffect,themajorfactor）；Hydrogenbondbetweencomplementarybasepairs；electrovalentbond（betweenthenegativechargescarriedonthephosphategroupsandthepositivechargescarriedontheproteinsormetalions）,2.1.2.2Conformationpolymorphismofthedoublehelix,Alternativedouble-helicalstructuresofDNA,B-form：relativehumidityis92%A-form：relativedevoidofwater(under75%)Z-form：lefthandedhelixH-form：triplehelix,1953,WatsonTm（meltingtemperature):Temperaturewhen50%DNAdenaturationTmisacharacteristicconstantofDNA,94,2.2.1.2Renaturation,Definition：annealing。,D.SDNA,S.SDNA,Denaturation,Renaturation,DependsonthecollisionofcomplementaryS.S.DNA,2.2.1.3renaturationdynamics,DNA复性过程遵循二级反应动力学DNA复性过程中单链消失的速度用公式表示：-dC/dt=kC2,C/C0=1/(1+kC0t),其中，C是单位时间的单链DNA的浓度C0为开始反应时变性解链的单链DNA浓度，t为复性时间K是复性速度常数（L/mols），k取决于阳离子浓度、温度、pH值、DNA片段大小。,C0t曲线,Definition：therenaturationofregionsofcomplementaritybetweendifferentnucleicacidstrands(DNAorRNA)Characteristic：sensitive、specific,HybridizationofNucleicAcids,RNA,DNA1,DNA2,DNA,Southernhybridization,Northernhybridization,JuangRH(2004)BCbasics,Probe,SouthernblottingNorthernblottingdotblotinginsituhybridizationWesternblotting,HybridizationofNucleicAcids,Southernblotting,电转印法,NorthernBlotting,dotblotting,DenaturedDNAorRNAsampleswereapplieddirectlyonamembraneasadot,thenfollowedbydetectionbyeithernucleotideprobes.,insituhybridization,Definition：atypeofhybridizationthatusesalabeledcomplementaryDNAorRNAstrand(i.e.,probe)tolocalizeaspecificDNAorRNAsequenceinaportionorsectionoftissue(insitu).,FISHInacistron,therearemanycrossingoversites(recons).Ageneisacistron,consistingofmanymutonsandrecons.,2.3.2.3Structuralgeneandregulatorygene,Operontheory(1961,JacobF.acompletegeneticsequenceononesetofchromosomes.,MaximumC-value:thequantityofDNAinthe(haploid)genome.MinimumC-value:theminimumgenomesizerequiredtomakeorganisms.,GenomesizeisthetotalamountofDNAcontainedwithinonecopyofasinglegenome.,C-valueparadox,C-valueparadoxreferstothelackofacorrelationbetweengenomesize(C-value)andgeneticcomplexity.Theminimumgenomesizefoundineachphylumincreasesfromprokaryotestomammals.Therearewidevariationsinthegenomesizesoforganismswithinmanyphyla,suchasinsects,amphibiansandfloweringplants.HighereukaryoteshavemuchmoreDNAthanthey“actuallyneed”.,E.coli,Humansgenome,Small;Asingleclosed-circularDNA；Genesarenaked；Mostsequencesencodegeneticinformation；Regulationunitsofgeneexpression-operons；overlappinggenes.,2.6.2.1Propertiesofprokaryoticgenome,Muchlargerthanprokaryoticchromosomegenome；HighlyorganizedcomplexofDNAandprotein,knownaschromatin,isconsistingofnuclesomes；Eachchromosomehasmultipleorigins；alargerproportionofeukaryoticgenomedoesnotencodeusefulgeneticinformationnon-codingDNA(tandem、interspersed)；RepetitiveDNA；Thecodingregionsofgenesconsistpredominantlyofsingle-copygenes,whichtranscribedmonocistrons,2.6.2.2proper