分子生物学第1章绪论

IntroductiontoMolecularDepartmentofBiochemistryandMolecularBiology,CCMUE-mail: WhatisMolecularBriefHistoryofMolecularMainTopicsinMolecular WhatisMolecularTheattempttounderstandbiologicalphenomenaThestudyofgenestructureandfunctionatthemolecularlevel.Asaresult,itisthestudyofmolecularbasicoftheprocessofreplication,transcriptionandtranslationofthegeneticmaterial.MolecularbiologymainlyconcernsitselfUnderstandingofin ctionsbetweenthevarioussystemsofacell,includingthein ctionsbetweenDNA,RNAandproteinbiosynthesisLearninghowthese ctionsareMainComponentsInvolveinMolecularBiologyAllLifedependson3criticalmacromolecules(3个重要的大分子DifferenceDifferencesandrelationsamongMolecularBiology,BiochemistryandGeneticsMolecularBiology:morefocusedonthemolecularbasisofbiology,especiallymacromolecules;Biochemistry:organicchemistry,thechemicalbasisoflife;Genetics:humangenome,inheritanceofdiseases,chromosomalabnormalitiesMolecularThisfieldoverlapswithotherareasofbiologyandchemistry,particularlygeneticsandbiochemistry.ItisthejoiningofaspectsbetweengeneticsandSomeSomeTerminologyNucleicacid:Biologicalmolecules(RNAandDNA)thatalloworganismstoreproduce（一些名词BasicphysicalandfunctionalunitsofhereditylocatedonthechromosomesconsistingofspecificsequencesofDNAbases;GensencodeinstructionsonhowtomakeGenotype:Genotype:ThegeneticmakeupofanPhenotypePhenotype:thephysicalexpressedtraitsofanABriefHistoryofMolecularFocusonhowDNAwasidentifiedasgeneticmatGenes,Genes,proteinsandAnineteenth-centurymonkcalledGregorMendelintroducedthenotionofgenes:basicunitsresponsibleforpossessionandpassingonofasinglecharacteristicInitiallyitwasthoughtthatproteinscarriedgeneticinformationUntilmid20th-century,whenitwasfoundDNAProteinsarethefunctionalmoleculesincells(ie.theyperformthemajorityofthereactionsoflife)TheexistenceofgeneswasfirstsuggestedbyGregorMendel(1822–1884),who,inthe1860s,studiedinheritanceinpea nts(Pisumsativum)andHehypothesizedafactorthatconveystraitsfromparenttooffspring.Hespentover10yearsofhislifeononeAlthoughhedidnotusethetermgene,heexinedhisresultsintermsofinheritedInitiallyitwasthoughtthatproteinscarriedgeneticBut,whatisthegeneticmaterial,DNAor3Griffith’sAvery–MacLeod–McCartyGriffith'sFrederickGriffithGriffith’sexperiment(格里菲斯实 型，无毒性）。其中III-S型具有以多糖免疫系统，进而使宿主 。II-Ro oniae(p growingascoloniesonthesurfaceofaculturemedium.Left:Thepresenceofacapsulearoundthebacterialcellsgivesthecoloniesaglistening,smooth(S)appearance.Right: coccilackingcapsuleshaveproducedtheserough(R)colonies.(CourtesyofRobertAustrian,J.Exp.Med.98:21,Left:Aneutrophilextendsapseudopodtowardtwop Center:thesebacteriahavebeenengulfed(arrows),andtheneutrophilisbeginningtoengulffourmorep ococciattheupperright.Right:Twop ococcihaveescaped.(FromW.B.Wood,M.R.Smith,andB.Watson,JournalofExperimentalMedicine84:387,1946.)Griffith's

Griffith'sexperimentdiscoveringthe"transformingprinciple" ococcus Purificationofactivematerialsfrom ococcus(smoothcolonies)

OswaldAveryandhiscolleaguesatTheRockefellerInstituteinNewYorkCityeventuallyshowedthatthe"something"wasDNA.InpursuingGriffith'sdiscovery,theyfoundthattheycouldbringaboutthesamekindoftransformationinvitrousinganextractofthebacterialTreatingthisextractwithenzymestoallpolysaccharides(includingthepolysaccharideofthealipasetodestroyanyproteasestodestroyallRNasetodestroydidnotdestroytheabilityoftheirextractstotransformtheButtreatingtheextractswithDNasetodestroytheDNAinthemdidabolishtheirtransformingactivity.SoDNAwastheonlymaterialinthedeadcellscapableoftransformingcellsfromonetypetoanother.DNAwasthesubstanceofgenes.Thiselectronmicrograph(courtesyofDr.AlexanderTomasz)showsaDNAmoleculeenteringa ococcus(thelargeobjectatthetop).ThisDNAmolecule—onlyaportionofwhich(scrolldown)isshownhere—is inlength,longenoughtoincludeadozengenes.TheprocessoftransformationfollowstheuptakeofsuchamoleculebytheTheHershey-ChaseExperimentAlfredHersheyandMarthaChasefurtheredresearchin1952withtheHershey-ChaseT2HersheyChase DNAasGeneticMaterial( HersheyandChase,usedbacteriophageT2infectionasDNAlabeledwith32P;proteincoatlabeledwithOnlyDNAenteredcellbutbothnewDNAandproteincoatssynthesizedandincorporatedintonew indicatingthatDNAhadthegeneticinformationforsynthesisofbothoftheseviralcomponentsDNADNAisthegeneticTheseexperimentspavedtheforWatsonandCrick'sdiscoveryofthehelicalstructureofDNA,andthusthebirthofmoderngeneticsandmolecularChargaff‘srules 法则

EdwinThefirstandbestknownachievementwastoshowthatinnaturalDNAthenumberofguanineunitsequalsthenumberofcytosineunitsandthenumberofadenineunitsequalsthenumberofthymineunits.ThecompositionofDNAvariesfromonespeciestoanother,inparticularintherelative

DNA双螺旋形结amountsofA,GTandCbasesSuchevidenceofmoleculardiversity,whichhad

crediblecandidateforthegeneticmaterialthanprotein.

TheTheRacefortheDoubleWatsonandCrickformedanunlikelypartnershipA22yearoldPhDandathirty+PhD“wanttobe”embarkedonamodelmakingventureatUsedtheresearchofotherscientiststodeterminethenatureofthedoublehelixTheRacefortheDoubleRosalindFranklin(罗沙 克林)andMauriceWilkinsKingsCollegeStudiedtheAandBformsofDNARosalind’sfamousx-raycrystallographypictureoftheBformheldthesecret,butshedidn’trealizeitssignificanceRosalindTechnicallyandRosalindFranklin(1920-FocusedontheRosalindFranklin(1920-GeneticKnowledgeofthestructureofDNAledscientiststoexaminethenatureofgeneticcodingand,inturn,understandtheprocessofprotein

andHeinrichMatthaeiwerethefirsttoelucidatethenatureofacodonin1961attheNationalInstitutesofHealth.Theyusedacell-systemtotranslateapoly-uracilRNAsequence(i.e.,UUUUU...)anddiscoveredthatthepolypeptidethattheyhadsynthesizedconsistedofonlytheamino

HarGobindRibonucleicacid(RNA)withthreerepeatingunits(UCUCUCU→UCUCUCUCU)producedtwoalternatingaminoacids.This,combinedwiththeNirenbergandLederexperiment,showedthatUCUcodesforSerineandCUCcodesforLeucine.RNAswiththreerepeatingunits(UACUACUA→UACUACUAC,orACUACUACU,orCUACUACUA)producedthreedifferentstringsofaminoacids.RNAswithfourrepeatingunitsincludingUAG,UAA,orUGA,producedonlydipeptidesandtripeptidesthusrevealingthatUAG,UAAandUGAarestopGeneSincethen,muchresearchhasbeenconductedtomodulatestepsinthegeneexpressionprocess.Thesestepsincludetranscription,RNAsplicing,translation,andpost-translationalmodificationwhichareusedtocontrolthechemicalandstructuralnatureofproteins.[12]MajoreventsinthehistoryofMolecularBiology 1952-19601956GeorgeEmilPaladeshowedthesiteofenzymesmanufacturinginthe smismadeonRNAGeorgeEmil Moreover,geneticengineeringgivesengineerstheabilitytodirectlymanipulatethegeneticmaterialsoforganismsusing binantDNAtechniques. binantDNAmoleculewascreatedbyPaulBergin1972whenhecombinedDNAfromthemonkeySV40withthatofthelambda MajoreventsinthehistoryofMolecularBiology19701970HowardTeminandfirstrestrictionenzymeThismeansthat:DNAcanbecutintoreproduciblepiecesatspecificsitebyrestrictionenzymescalledThepiecescanbelinkedtobacterialvectorsandintroducedintobacterialThisiscalled(genecloningorbinantDNAtechnology)Biology1970-1977MajoreventsinthehistoryBiology1970-19771977PhillipSharpandRicharddemonstratedthatpre-mRNA1977PhillipSharpandRicharddemonstratedthatpre-mRNAisprocessedbytheexcisionofintronsandexonsaresplicedtogether.MajoreventsinthehistoryofMolecularBiology1986-19951986LeroyHood:Developedautomatedsequencing1986HumanGenomeInitiativeofchromosomes3,11,12,and22wereThesemapsprovidethelocationsof“markers”oneachchromosometomakelocatinggeneseasier

Leroy1996First1996Firsteukaryoticgenome-MajoreventsinthehistoryofMolecularBiology1995-19961995John1995JohnCraigVenter:Firstbacterialgenomessequenced1995AutomatedfluorescentsequencinginstrumentsandroboticoperationsJohnCraigBiologyMajoreventsinthehistoryofMolecularBiologyMolecularMolecularBiology1997-1999Firsthumanchromosome(number22)MolecularMolecularBiology2000-2001InternationalHumanthefirstdraftofthesequenceofthehumangenomeBiology2003-PresentApril2003HumanGenomeProjectCompletedMousegenomeisBiology2003-PresentApril2003HumanGenomeProjectCompletedMousegenomeisApril2004RatgenomegenomesbeingsequencedbyIII.III.MainTopicsofMolecular GeneexpressionandStructureandfunctionofbiologicalGenomics,proteomics,IV.IV.What’s FromReductionlismtoHolism:Omicsandsystembiology GenefunctionsandapplicationtoMedicineandSociology(ie.Drugeffectsandtoxicitiesareusuallycausedbymultiplegeneticfactors,betterunderstandingthehumangenomeisMolecular