分子生物學英文課件：chapter1 Structure

MolecularBiology

MolecularBiologyContentsofmolecularbiologyNucleicacidandnucleotidesGeneexpression?SynthesisofDNA(replication)?SynthesisofRNA(transcription)?Synthesisofprotein(translation)RegulationofgeneexpressionGeneticengineeringSignaltransductionContentsofmolecularbiologyResearchHistoryofMolecularBiologyResearchHistoryIn1869,F.Miescher:nucleinIn1928,FredGriffith:transformationIn1944,Averyandhiscolleges:DNA——geneticmaterialIn1953,WatsonandCrick:DNAdoublehelicalmodelIn1957,Kornberg:DNApolymeraseⅠIn1958,Crick:thecentraldogmaIn1961,JacobandMonod:operontheoryIn1966,Nirenberg、OchoaandKhorana:thegeneticcodonIn1970,TeminandBaltimore:reversetranscriptaseIn1869,F.Miescher:nuclein

somesubstancefromtheheat-killedScellshadbeenpickedupbysomeoftheRcells,changingthemintovirulentStypecells.Griffithcoinedtheterm"transformation"todescribethisprocess.1928byFredGriffithsomesubstancefromtheIn1967-1970,R.YuanandH.O.Smith:RestrictionendonucleaseIn1975-1977,Sanger、MaxamandGilbert:DNAsequencingIn1990s,automaticDNAsequencingIn1981,Cech:rRNAselfsplicing－ribozymeIn1981,thefirsttransgenicmiceIn1985,Mullis:PCRIn1990,HGPlaunchedIn1990,ADAdeficiencygenetherapyIn1996,“Dolly”sheepIn1998,AndrewZ.FireandCraigC.Mello:RNAi(2006Nobelprize)

In2001,PublishingofthedraftversionoftheHumanGenome分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureTransgenicMouse,1982AchievementsofgeneengineeringTransgenicplantTransgenicAchievementsofgene克隆羊“多莉”克隆羊“多莉”的研究者伊恩·維爾穆特（Wilmut）

Nucleustransferringcloning克隆羊“多莉”克隆羊“多莉”的研究者Nucleustran分子生物學英文課件：chapter1StructureBiochipHumanGenomeProjectBiochipHumanGenomeProjectDNARNAProteinTheCentralDogmaReplicationTranscriptionTranslationReversetranscriptionDNAandproteinDNARNAProteinTheCentralDogmaChapter1

structureandfunction

ofnucleicacidChapter1

structureandfuncNucleicacidsarebiologicalinformationmacromoleculesClassification:Deoxyribonucleicacid,DNA:presentinnucleusandmitochondria;storeandcarrygeneticinformation.Ribonucleicacid,RNA:

presentincytoplasmandnucleus;involvedinexpressionofgeneticinformation.NucleicacidsarebiologicaliSectionIChemicalcompositionandprimarystructureofnucleicacid

SectionINucleotidesarebasiccomponentunitsofnucleicacid(RNA)(DNA)nucleotideBasePentosephosphateNucleotidesarebasiccomponenBasePurinepyrimidineAdenine,AGuanine,GCytosine,CThymine,TUracil,UPresentinbothDNAandRNA(OnlyinDNA)(OnlyinRNA)I.ChemicalcompositionofnucleotidesBasePurinepyrimidineAdenine,分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure酮式烯醇式互變異構酮式烯醇式互變異構胺式

亞胺式互變異構胺式

亞胺式互變異構Pentose:riboseinRNA,deoxyriboseinDNAPentose:riboseinRNA,TheprincipalderivativesofpurinesandpyrimidinesarenucleosidesandnucleotidesNucleoside=base(PurineoraPyrimidine)+pentose(riboseordeoxyribose)riboseribonucleoside2’-deoxyribosedeoxyribonucleosidepurinepurinenucleosidePyrimidinepyrimidinenucleosideTheprincipalderivativesofpBaseandribose(deoxyribose)arelinkedviaaglycosidicbond:Baseandribose(deoxyribose)aARCRARNucleotide=nucleoside+phosphateor=Base(purineorpyrimidine)+pentose(riboseordeoxyribose)+phosphateriboseribonucleotide2’-deoxyribose deoxyribonucleotidePurinepurinenucleotidePyrimidinepyrimidinenucleotideNucleotidesarephosphorylatednucleosidesNucleotide=nucleoside+phosEsterbondNucleosidesandphosphatesarelinkedbyesterbond:EsterbondNucleosidesandphosEsterbondglycosidicbondEsterbondglycosidicbond分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureTypesofribonucleotidesanddeoxyribonucleotides

TypesofribonucleotidesanddDerivativesofnucleotideDerivativesofnucleotideII.

primarystructureofnucleicacid

Theprimarystructureisthesequenceofnucleosidemonophosphatesfrom5’endto3’endinnucleicacid.(usuallywrittenasthesequenceofbases).

PhosphodiesterbondII.primarystructureofnucl分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureWrittenfrom5to3:Writtenfrom5to3:basepentoseDNAA、G、C、TdeoxyriboseRNAA、G、C、UriboseThedifferencesbetweenDNAandRNA:basepentoseDNAA、G、C、TdeoxyriboSectionII

Spatial

structureandfunctionofDNASectionII

Chargaff'sRules:

purines=pyrimidinesA=TG=CX-raydiffractionstudiesofFranklinandWilkinsHelixmoleculeDoublestrandsBackgroundsofpropositionofdoublehelixI.ThesecondarystructureofDNA—doublehelixmodelChargaff'sRules:Backgrounds分子生物學英文課件：chapter1Structure5′5′

3′

3′MinorgrooveMajorgroove5′5′3′3′MinorgrooveMajorgr分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureAntiparallelcomplementorydoublehelixstrand.Basepairing:A-TC-G

Pentose-phosphatebackboneoutsideandbasepairsinside.

Stabilizedbyhydrogenbondandbasestackingforce.geneticinformationconsistsintheDNAbasesequencesAntiparallelcomplementorydou1.

Twopolynucleotidechains,right-handeddoublehelix.2.ThetwostrandsofDNAareantiparallel.3.Pentose-phosphatebackboneoutsideandbasepairsinside4.Thesurfaceofthedoublehelixcontainstwogrooves:themajorandminorgrooves.5.Eachbaseishydrogenbondedtoabaseintheoppositestrandtoformabasepair.Theplanesofbasepairareperpendiculartoitsaxis.(ApairswithT;GpairswithC)6.thediameteris2.37nm,thepitchofaturnis3.54nm,10.5basepairsperturn,thedistancebetweentwobaseplanesis0.34nm.7.stabilizingforce:hydrogenbondandbasestackingforcePointsofDNAdoublehelicalmodel:1.Twopolynucleotidechains,DifferenttypesofDNA:DifferenttypesofDNA:ThedifferencesofthreetypesofDNA

A-DNAB-DNAZ-DNAhelixdiameterbp/perturnnm/perturnbackboneRight-handed2.55nm11bp2.53nmlinearRight-handed2.37nm10.5bp3.54nmlinearLeft-handed1.84nm12bp4.56nmzigzagThedifferencesofthreetypesTriplexDNAInthesetriplehelices,thethirdstrandremainsassociatedwithduplexDNAthroughnon-Watson-CrickinteractionsnowknownasHoogsteenpairing.

N6TriplexDNAInthesetripleheStructureofaG-quadruplex.Left:aG-tetrad.Right:anintramolecularG-quadruplexStructureofaG-quadruplex.

II.SupercoiledstructureofDNAinprokaryotesII.SupercoiledstructureofrelaxedsupercoiledTelephonecordrelaxedsupercoiledTelephoneco

III.nucleosomeineukaryotesnucleosomeIII.nucleosomeineukaryotesNucleosome:

ThebindingofDNAbythehistonescreatesastructureunitofchromatin,thestructureunitiscallednucleosome.NucleosomelinkerNucleosomecore

HistoneH160bpofDNAOctamerofhistone(twomoleculeseachofH2A、H2B、H3、H4)150bpofDNANucleosome:ThebindingofDNAH1histoneH1histone分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure

IV.FunctionofDNA:*DNAiscarrierofgeneticinformation.Itcantransfergeneticinformationbyreplication.*Gene：Inmolecularterms,itisafunctionalsegmentofDNAthatcodesforpolypeptidechainorRNAmolecules.

*

Genomeisthetotalgeneticinformationofanorganism.Formostorganisms,itisthecompleteDNAsequence.IV.FunctionofDNA:*DNAis分子生物學英文課件：chapter1StructureThechemicalnatureofRNAdiffersfromthatofDNAInRNA,thesugarisriboseratherthan2-deoxyriboseofDNA.Insteadofthymine,RNAcontainstheuracil.RNAexistsasasinglestrand,whereasDNAexistsasadouble-strandedhelicalmolecule.InRNA,guaninecontent≠cytosinecontent;adeninecontent≠uracilcontent.

SectionIII.StructureandfunctionofRNA

ThechemicalnatureofRNAdif參與蛋白質合成的三種主要RNA：

messengerRNAs(mRNAs,~5%oftotalRNA)TransferRNAs(tRNAs,~15%oftotalRNA)RibosomalRNAs(rRNAs,~80%oftotalRNA)參與蛋白質合成的三種主要RNA：

I.StructureandfunctionofmRNAThemostheterogeneousinsizeandstability.Serveastemplatesofproteinsynthesis.Uniquecharacteristics(ineukaryote):

capof5’-terminal(7-mGpppNm)tailof3’-terminal(polyA)

I.StructureandfunctionofmRNAstructureinprokaryotes5’

3’StartcodonAUGstopcodonCodingregiontriplet5'untranslated

region3'untranslated

region?AGGA?Shine-Dalgarno(SD)sequence(Ribosomalbindingsite,RBS)SDsequence(RBS)isasequenceupstreamthestartcodeinprokaryoticmRNAthatcanbase-pairstoa?UCCU?sequenceatorverynearthe3'endof16SrRNA,therebybindingthemRNAandsmallribosomalsubunittoeachother.mRNAstructureinprokaryotes5mRNAstructureineukaryotes5'm7Gppp

CapAAA???AAA3‘PolyAtailStartcodonAUGstopcodonCodingregiontriplet

CapRecognizedandboundbyCBP(cap-sitebindingprotein)duringinitiationoftranslationPolyAtailrecognizedandboundbyPAB(polyAbindingprotein)5'untranslatedregion3'untranslatedregionmRNAstructureineukaryotes5'…..…CTCCTAGTACGATCGT….CTAGTCATTCGGTA…DNA5’cap..GAGGAUCAUGCUAGCA….GAUCAGUAAGCCAU...AAAAA…..mRNA

N-aa1aa2aa3……aaaa-C5’UTRCodingregion3’UTR3’polyAtail…..…CTCCTAGTACGATCGT….CTAGTCcappingenzyme5′，5′-GpppG-cappingenzyme5′，5′-GpppG-AATAAATTATTTGUGTCADNAmRNAAATAAATTATTTGUGTCADNAmRNA分子生物學英文課件：chapter1Structure7-mGpppNmcanbindwithCBPsFunctionsof5’capstructure(7-mGpppNm):Functionsof3’tail(polyA):polyAbindwithPABPCBP:capbindingprotein，帽結合蛋白PABP:poly(A)-bindingprotein,多聚腺苷酸結合蛋白-translocationofmRNAfromnucleartocytoplasm-regulatingtheinitiationoftranslation-increasingthestabilityofmRNA7-mGpppNmcanbindwithCBPsFTableforgeneticcodonTableforgeneticcodon分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructurehnRNASplicinghnRNASplicing分子生物學英文課件：chapter1StructureTheroleofmessengerRNAs(mRNA):astemplate*ThisclassofRNAservesasthetemplatesusedtodeterminethesequenceofaminoacidsinproteinsynthesis.*InamRNA,beginningfromthefirstAUGthatissaidtobetheinitiationsignal(asainitiationcondon)everysubsequenttripletbasesisreadasacondonuntilreachingastopcondon(UAA,UGA,UAG).Openreadingframe(ORF)

5'CGGAAUG

GCA

GAG

UGG

CUA

UAAGCAUG

MetAlaGluTrpLeu

*Eachcodonspecifiesanaminoacid.ItisthecodonsequenceofamRNAthatdeterminestheaminoacidsequenceofaprotein.TheroleofmessengerRNAs(mRVaryinlengthfrom74to95nucleotides.Containsmorerarebases.Serveascarrierofaainthetranslation.

II.Structureandfunctionof

tRNArarebases(C-C-glycosidicbond)Varyinlengthfrom74to95nrarebasesrarebasesFeaturesofsecondarystructureoftRNA:cloverleafFourloops:Dloop,anticodonloop,variableloop,andTψCloopFourarms:acceptorarm,Darm,TψCarm,andanticodonarmDDDFeaturesofsecondarystructurSecondarystructure(cloverleaf)Tertiarystructure(inverse“L”)DDDSecondarystructure(cloverleTherolesoftransferRNAs(tRNAs):asanadaptertRNAsfunctionasanadaptermoleculeinvirtueofformingcovalentattachmentofindividualaminoacidcatalyzedbyaminoacyl-tRNAsynthetaseandrecognizingthecodonsequencesofthemRNAstoallowcorrectinsertionofaminoacidsintotheelongatingpolypeptidechain.TherolesoftransferRNAs(tR分子生物學英文課件：chapter1Structuresubunitprokaryotes

（70S）eukaryotes

（80S）SproteinsrRNASproteinsrRNASmallersubunit3021kinds16S4033kinds18SLargersubunit5031kinds23S5S6050kinds28S5.8S5SComponentsofribosomesIII.Structureandfunctionof

rRNAsubunitprokaryotes（70S）eukary分子生物學英文課件：chapter1Structure真核生物18SrRNA真核生物18SrRNA原核生物翻譯過程中核糖體結構模式:氨基酰位（aminoacylsite，A位）肽酰位（peptidylsite，P位）排出位（exitsite，E位）原核生物翻譯過程中核糖體結構模式:氨基酰位肽酰位排出位（exThethreerolesofRNAinproteinsynthesis.MessengerRNA(mRNA)istranslatedintoproteinbythejointactionoftransferRNA(tRNA)andtheribosome,whichiscomposedofnumerousproteinsandtwomajorribosomalRNA(rRNA)moleculesThethreerolesofRNAinprotⅣ.Othernon-codingRNA(ncRNA)

longnon-codingRNAandsmallnon-codingRNASnRNA(smallnuclearRNA)SnoRNA(smallnucleolarRNA)ScRNA(smallcytoplasmRNA)siRNA(smallinterferingRNA)

MicroRNAs

SmallcatalyticRNA:

Ribozymes,aretheRNAmoleculeswithcatalyticactivity.

Theactivityoftheseribozymesofteninvolvesthecleavageofanucleicacid.

RNAinterference(RNAi)被《Science》評為2002年最重大科技突破。Ⅳ.Othernon-codingRNA(ncRNASmallinterferingRNA(siRNA)siRNAsstructure:ashort(usually21-nt)double-strandofRNA(dsRNA)with2-nt3'overhangsoneitherend.SmallinterferingRNA(siRNA)分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureRibozymeAnRNAmoleculewithcatalyticactivitySecondarystructureofribozyme------HammerheadstructureRibozymeSecondarystructureof分子生物學英文課件：chapter1StructureSectionⅣPhysicalandchemicalfeaturesofnucleicacidandapplications

Ⅰ.Generalfeaturesofnucleicacid:AcidityViscosityConformationAbsorbanceof260nmSectionⅣⅠ.Generalfeatures1.DNA或RNA的定量A260=1.0相當于50μg/ml雙鏈DNA40μg/ml單鏈DNA（或RNA）20μg/ml寡核苷酸2.判斷核酸樣品的純度DNA純品:A260/A280=1.8RNA純品:A260/A280=2.0A260的應用目錄1.DNA或RNA的定量A260的應用目錄Definition:

DNAdenaturationmeansthataDNAhaslostits’nativeconformationanddoublestrandDNAisseparatedtosinglestrandDNAbyexposedtoadestabilizingfactorsuchasheat,acid,alkali,ureaoramide.(whenhightemperatureisusedtodenatureDNA,theDNAissaidtobemelted).Ⅱ.DenaturationofDNADefinition:DNAdenaturationmDNAmeltingcurve:Tm

ismeltingtemperatureatwhichhalf(50%)ofDNAmoleculesaredenaturedDNAmeltingcurve:TmismeltinTmisproportionalto(G+C)%ofDNAmoleculesTm=69.3+0.41×(G+C)%DNAlengthThefactorsofinfluencingTm:Tmisproportionalto(G+C)%oDouble-strandedSinglestrandedDefinition:Hyperchromiceffect:Double-strandedSinglestrandedDNArenaturation:RemovingthedenaturationfactorsorinproperconditionthedenaturedDNA(ssDNA)restorenativestructure(dsDNA)andfunction.TheprocessofrenaturationofheatdenaturedDNAbyslowlycoolingiscalledannealingⅢ.RenaturationandhybridizationDNArenaturation:Ⅲ.Renaturat分子生物學英文課件：chapter1StructureHybridization:whenheterogeneousDNAorRNAareputtogether,theywillbecometoheteroduplexviathebase-pairingrulesduringrenaturationiftheyarecomplementaryinparts(notcomplete).Thisiscalledmolecularhybridization.Hybridization:分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureSectionⅤNucleasesdeoxyribonucleasesribonucleasesEndonucleases:restrictionendonucleasesexonucleases5′exonucleases3′exonucleasesSectionⅤNucleasesdeoxyribonPalindrome

--thesamesequencesinthe

（rotationalsymmetry)5'→3'directionofbothstrandsEcoRI

PstI

HpaI

5'3'3'-GACGTC--CTGCAG-5'5'3'-GAATTC-5'3'-CTTAAG-5'5'3'3'-GTTAAC--CAATTG-5'overhangstickyend

3'overhangstickyendbluntend

Restrictionendonucleases

RecognizespecificnucleotidesequencesandcleaveDNAPalindrome--thesamesequ*切割后可形成平頭末端或粘性末端平頭末端Bluntend:粘性末端Stickyend:SamI*切割后可形成平頭末端或粘性末端SamI5’突出的粘性末端:3’突出的粘性末端:5’突出的粘性末端:3’突出的粘性末端:StickyendsareparticularusefulinconstructingrecombinantorchimericDNAmolecules.Stickyendsareparticularuse5’→3’polymerizingactivity5’→3’exonucleaseactivity5’→3’polymerizingactivity55’→3’polymerizingactivity3’→5’exonucleaseactivity5’→3’polymerizingactivityDNAdenaturationMolecularHybridizationHyperchromiceffectORF分子生物學英文課件：chapter1StructureMolecularBiology

MolecularBiologyContentsofmolecularbiologyNucleicacidandnucleotidesGeneexpression?SynthesisofDNA(replication)?SynthesisofRNA(transcription)?Synthesisofprotein(translation)RegulationofgeneexpressionGeneticengineeringSignaltransductionContentsofmolecularbiologyResearchHistoryofMolecularBiologyResearchHistoryIn1869,F.Miescher:nucleinIn1928,FredGriffith:transformationIn1944,Averyandhiscolleges:DNA——geneticmaterialIn1953,WatsonandCrick:DNAdoublehelicalmodelIn1957,Kornberg:DNApolymeraseⅠIn1958,Crick:thecentraldogmaIn1961,JacobandMonod:operontheoryIn1966,Nirenberg、OchoaandKhorana:thegeneticcodonIn1970,TeminandBaltimore:reversetranscriptaseIn1869,F.Miescher:nuclein

somesubstancefromtheheat-killedScellshadbeenpickedupbysomeoftheRcells,changingthemintovirulentStypecells.Griffithcoinedtheterm"transformation"todescribethisprocess.1928byFredGriffithsomesubstancefromtheIn1967-1970,R.YuanandH.O.Smith:RestrictionendonucleaseIn1975-1977,Sanger、MaxamandGilbert:DNAsequencingIn1990s,automaticDNAsequencingIn1981,Cech:rRNAselfsplicing－ribozymeIn1981,thefirsttransgenicmiceIn1985,Mullis:PCRIn1990,HGPlaunchedIn1990,ADAdeficiencygenetherapyIn1996,“Dolly”sheepIn1998,AndrewZ.FireandCraigC.Mello:RNAi(2006Nobelprize)

In2001,PublishingofthedraftversionoftheHumanGenome分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureTransgenicMouse,1982AchievementsofgeneengineeringTransgenicplantTransgenicAchievementsofgene克隆羊“多莉”克隆羊“多莉”的研究者伊恩·維爾穆特（Wilmut）

Nucleustransferringcloning克隆羊“多莉”克隆羊“多莉”的研究者Nucleustran分子生物學英文課件：chapter1StructureBiochipHumanGenomeProjectBiochipHumanGenomeProjectDNARNAProteinTheCentralDogmaReplicationTranscriptionTranslationReversetranscriptionDNAandproteinDNARNAProteinTheCentralDogmaChapter1

structureandfunction

ofnucleicacidChapter1

structureandfuncNucleicacidsarebiologicalinformationmacromoleculesClassification:Deoxyribonucleicacid,DNA:presentinnucleusandmitochondria;storeandcarrygeneticinformation.Ribonucleicacid,RNA:

presentincytoplasmandnucleus;involvedinexpressionofgeneticinformation.NucleicacidsarebiologicaliSectionIChemicalcompositionandprimarystructureofnucleicacid

SectionINucleotidesarebasiccomponentunitsofnucleicacid(RNA)(DNA)nucleotideBasePentosephosphateNucleotidesarebasiccomponenBasePurinepyrimidineAdenine,AGuanine,GCytosine,CThymine,TUracil,UPresentinbothDNAandRNA(OnlyinDNA)(OnlyinRNA)I.ChemicalcompositionofnucleotidesBasePurinepyrimidineAdenine,分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure酮式烯醇式互變異構酮式烯醇式互變異構胺式

亞胺式互變異構胺式

亞胺式互變異構Pentose:riboseinRNA,deoxyriboseinDNAPentose:riboseinRNA,TheprincipalderivativesofpurinesandpyrimidinesarenucleosidesandnucleotidesNucleoside=base(PurineoraPyrimidine)+pentose(riboseordeoxyribose)riboseribonucleoside2’-deoxyribosedeoxyribonucleosidepurinepurinenucleosidePyrimidinepyrimidinenucleosideTheprincipalderivativesofpBaseandribose(deoxyribose)arelinkedviaaglycosidicbond:Baseandribose(deoxyribose)aARCRARNucleotide=nucleoside+phosphateor=Base(purineorpyrimidine)+pentose(riboseordeoxyribose)+phosphateriboseribonucleotide2’-deoxyribose deoxyribonucleotidePurinepurinenucleotidePyrimidinepyrimidinenucleotideNucleotidesarephosphorylatednucleosidesNucleotide=nucleoside+phosEsterbondNucleosidesandphosphatesarelinkedbyesterbond:EsterbondNucleosidesandphosEsterbondglycosidicbondEsterbondglycosidicbond分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureTypesofribonucleotidesanddeoxyribonucleotides

TypesofribonucleotidesanddDerivativesofnucleotideDerivativesofnucleotideII.

primarystructureofnucleicacid

Theprimarystructureisthesequenceofnucleosidemonophosphatesfrom5’endto3’endinnucleicacid.(usuallywrittenasthesequenceofbases).

PhosphodiesterbondII.primarystructureofnucl分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureWrittenfrom5to3:Writtenfrom5to3:basepentoseDNAA、G、C、TdeoxyriboseRNAA、G、C、UriboseThedifferencesbetweenDNAandRNA:basepentoseDNAA、G、C、TdeoxyriboSectionII

Spatial

structureandfunctionofDNASectionII

Chargaff'sRules:

purines=pyrimidinesA=TG=CX-raydiffractionstudiesofFranklinandWilkinsHelixmoleculeDoublestrandsBackgroundsofpropositionofdoublehelixI.ThesecondarystructureofDNA—doublehelixmodelChargaff'sRules:Backgrounds分子生物學英文課件：chapter1Structure5′5′

3′

3′MinorgrooveMajorgroove5′5′3′3′MinorgrooveMajorgr分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1StructureAntiparallelcomplementorydoublehelixstrand.Basepairing:A-TC-G

Pentose-phosphatebackboneoutsideandbasepairsinside.

Stabilizedbyhydrogenbondandbasestackingforce.geneticinformationconsistsintheDNAbasesequencesAntiparallelcomplementorydou1.

Twopolynucleotidechains,right-handeddoublehelix.2.ThetwostrandsofDNAareantiparallel.3.Pentose-phosphatebackboneoutsideandbasepairsinside4.Thesurfaceofthedoublehelixcontainstwogrooves:themajorandminorgrooves.5.Eachbaseishydrogenbondedtoabaseintheoppositestrandtoformabasepair.Theplanesofbasepairareperpendiculartoitsaxis.(ApairswithT;GpairswithC)6.thediameteris2.37nm,thepitchofaturnis3.54nm,10.5basepairsperturn,thedistancebetweentwobaseplanesis0.34nm.7.stabilizingforce:hydrogenbondandbasestackingforcePointsofDNAdoublehelicalmodel:1.Twopolynucleotidechains,DifferenttypesofDNA:DifferenttypesofDNA:ThedifferencesofthreetypesofDNA

A-DNAB-DNAZ-DNAhelixdiameterbp/perturnnm/perturnbackboneRight-handed2.55nm11bp2.53nmlinearRight-handed2.37nm10.5bp3.54nmlinearLeft-handed1.84nm12bp4.56nmzigzagThedifferencesofthreetypesTriplexDNAInthesetriplehelices,thethirdstrandremainsassociatedwithduplexDNAthroughnon-Watson-CrickinteractionsnowknownasHoogsteenpairing.

N6TriplexDNAInthesetripleheStructureofaG-quadruplex.Left:aG-tetrad.Right:anintramolecularG-quadruplexStructureofaG-quadruplex.

II.SupercoiledstructureofDNAinprokaryotesII.SupercoiledstructureofrelaxedsupercoiledTelephonecordrelaxedsupercoiledTelephoneco

III.nucleosomeineukaryotesnucleosomeIII.nucleosomeineukaryotesNucleosome:

ThebindingofDNAbythehistonescreatesastructureunitofchromatin,thestructureunitiscallednucleosome.NucleosomelinkerNucleosomecore

HistoneH160bpofDNAOctamerofhistone(twomoleculeseachofH2A、H2B、H3、H4)150bpofDNANucleosome:ThebindingofDNAH1histoneH1histone分子生物學英文課件：chapter1Structure分子生物學英文課件：chapter1Structure

IV.FunctionofDNA:*DNAiscarrierofgeneticinformation.Itcantransfergeneticinformationbyreplication.*Gene：Inmolecularterms,itisafunctionalsegmentofDNAthatcodesforpolypeptidechainorRNAmolecules.

*

Genomeisthetotalgeneticinformationofanorganism.Formostorganisms,itisthecompleteDNAsequence.IV.FunctionofDNA:*DNAis分子生物學英文課件：chapter1StructureThechemicalnatureofRNAdiffersfromthatofDNAInRNA,thesugarisriboseratherthan2-deoxyriboseofDNA.Insteadofthymine,RNAcontainstheuracil.RNAexistsasasinglestrand,whereasDNAexistsasadouble-strandedhelicalmolecule.InRNA,guaninecontent≠cytosinecontent;adeninecontent≠uracilcontent.

SectionIII.StructureandfunctionofRNA

ThechemicalnatureofRNAdif參與蛋白質合成的三種主要RNA：

messengerRNAs(mRNAs,~5%oftotalRNA)TransferRNAs(tRNAs,~15%oftotalRNA)RibosomalRNAs(rRNAs,~80%oftotalRNA)參與蛋白質合成的三種主要RNA：

I.StructureandfunctionofmRNAThemostheterogeneousinsizeandstability.Serveastemplatesofproteinsynthesis.Uniquecharacteristics(ineukaryote):

capof5’-terminal(7-mGpppNm)tailof3’-terminal(polyA)

I.StructureandfunctionofmRNAstructureinprokaryotes5’

3’StartcodonAUGstopcodonCodingregiontriplet5'untranslated

region3'untranslated

region?AGGA?Shine-Dalgarno(SD)sequence(Ribosomalbindingsite,RBS)SDsequence(RBS)isasequenceupstreamthestartcodeinprokaryoticmRNAthatcanbase-pairstoa?UCCU?sequenceatorverynearthe3'endof16SrRNA,therebybindingthemRNAandsmallribosomalsubunittoeachother.mRNAstructureinprokaryotes5mRNAstructureineukaryotes5'm7Gppp

CapAAA???AAA3‘PolyAtailStartcodonAUGstopcodonCodingregiontriplet

CapRecognizedandboundbyCBP(cap-sitebindingprotein)duringinitiationoftranslationPolyAtailrecognizedandboundbyPAB(polyAb