分子生物學第1章緒論

IntroductiontoMolecularWhatisMolecularBriefHistoryofMolecularMainTopicsinMolecular WhatisMolecularTheattempttounderstandbiologicalphenomenamolecularThestudyofgenestructureandfunctionatthemolecularlevel.Asaresult,itisthestudyofmolecularbasicoftheprocessofreplication,transcriptionandtranslationofthegeneticmaterial.MolecularbiologymainlyconcernsitselfUnderstandingofin ctionsbetweenthevarioussystemsofacell,includingthein ctionsbetweenDNA,RNAandproteinbiosynthesisLearninghowthese ctionsareMainComponentsInvolveinMolecularBiologyAllLifedependson3criticalDifferencesandrelationsamongMolecularBiology,BiochemistryandGeneticsMolecularBiology:morefocusedonthemolecularbasisofbiology,especiallymacromolecules;Biochemistry:organicchemistry,thechemicalbasisoflife;Genetics:humangenome,inheritanceofdiseases,chromosomalMolecularThisfieldoverlapswithotherareasofbiologyandchemistry,particularlygeneticsandbiochemistry.ItisthejoiningofaspectsbetweengeneticsandSome（一些名詞Nucleicacid:Biologicalmolecules(RNAandDNA)alloworganismstoBasicphysicalandfunctionalunitsoflocatedonthechromosomesconsistingofspecificsequencesofDNAbases;GensencodeinstructionsonhowtomakeGenotype:ThegeneticmakeupofanPhenotype:thephysicalexpressedtraitsofanABriefHistoryofMolecularFocusonhowDNAwasidentifiedasgeneticGenes,proteinsandAnineteenth-centurymonkcalledGregorMendelintroducedthenotionofgenes:basicunitsresponsibleforpossessionandpassingonofasinglecharacteristicInitiallyitwasthoughtthatproteinscarriedgeneticinformationUntilmid20th-century,whenitwasfoundDNAProteinsarethefunctionalmoleculesincells(ie.theyperformthemajorityofthereactionsoflife)TheexistenceofgeneswasfirstsuggestedbyGregorMendel(1822–1884),who,inthe1860s,studiedinheritanceinpea sativum)andHehypothesizedafactorthatconveystraitsfromparenttooffspring.Hespentover10yearsofhislifeononeAlthoughhedidnotusethetermgene,he resultsintermsofinheritedInitiallyitwasthoughtthatproteinscarriedgeneticBut,whatisthegeneticmaterial,DNAor3Griffith’sGriffith's In1928,FrederickGriffithshowedthatgenescouldbetransferred.InwhatisnowknownasGriffith'sexperiment,injectionsintoamouseofadeadlystrainofbacteriathathadbeenheat-killedtransferredgeneticinformationtoasafestrainofthesamebacteria,killingthe ，無毒性）。其中III-S型具有以 ，因此無法幸免于免疫系。 oniae(p growingascoloniesonthesurfaceofaculturemedium.Left:Thepresenceofacapsulearoundthebacterialcellsgivesthecoloniesaglistening,smooth(S)appearance.Right: ococcilackingcapsuleshaveproducedtheserough(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" Purificationofactivematerialsfrom ococcus(smoothcolonies)

andCrick)OswaldAveryandhiscolleaguesatTheRockefellerInstituteinNewYorkCityeventuallyshowedthatthe"something"wasDNA.InpursuingGriffith'sdiscovery,theyfoundthattheycouldbringthesamekindoftransformationinvitrousinganextractofthebacterialTreatingthisextractwithenzymestoallpolysaccharides(includingthepolysaccharideofthealipasetodestroyanyproteasestodestroyallRNasetodestroydidnotdestroytheabilityoftheirextractstotransformtheButtreatingtheextractswithDNasetodestroytheDNAinthemdidabolishtheirtransformingactivity.SoDNAwastheonlymaterialinthedeadcellscapableoftransformingcellsfromonetypetoanother.DNAwasthesubstanceofgenes.ofDr.AlexanderTomasz)showsaDNAmoleculeenteringa ococcus(thelargeobjectatthetop).ThisDNAmolecule—onlyaportionofwhich(scrolldown)isshownhere—is inlength,longenoughtoincludeadozengenes.TheprocessoftransformationfollowstheuptakeofsuchamoleculebytheTheHershey-ChaseExperimentAlfredHersheyandMarthaChasefurtheredresearchin1952withtheHershey-ChaseT2HersheyChase DNAasGeneticMaterial( HersheyandChase,usedbacteriophageT2infectionasDNAlabeledwith32P;proteincoatlabeledwithOnlyDNAenteredcellbutbothnewDNAandproteincoatssynthesizedandincorporatedintonew indicatingthatDNAhadthegeneticinformationforsynthesisofbothoftheseviralcomponentsDNAisthegeneticTheseexperimentspavedtheforWatsonandCrick'sdiscoveryofthehelicalstructureofDNA,andthusthebirthofmoderngeneticsandmolecularChargaff‘srules（查戈夫法則

EdwinThefirstandbestknownachievementwastoshowthatinnaturalDNAthenumberofguanineunitsequalstheofcytosineunitsandthenumberofadenineunitsequalsthenumberofthymineunits.ThecompositionofDNAvariesfromonespeciestoanother,inparticularinthe

amountsofAGTandCbasesSuchevidenceofmoleculardiversity,whichhad

crediblecandidateforthegeneticmaterialthanprotein.

TheRacefortheDoubleWatsonandCrickformedanunlikelypartnershipA22yearoldPhDandathirty+PhD“wanttobe”embarkedonamodelmakingventureatUsedtheresearchofotherscientiststodeterminethenatureofthedoublehelixTheRacefortheDoubleRosalindFranklin(羅沙 克林)andMauriceWilkins(莫里斯威爾金斯atKingsCollegeStudiedtheAandBformsofDNARosalind’sfamousx-raycrystallographypictureoftheBformheldthesecret,butshedidn’trealizeitssignificanceRosalindTechnicallyandscientificallyagiftedRosalindFranklin(1920-RosalindFranklin(1920-GeneticKnowledgeofthestructureofDNAledscientiststoexaminethenatureofgeneticcodingand,inturn,understandtheprocessofprotein

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

HarGobindRibonucleicacid(RNA)withthreerepeatingunits(UCUCUCU→UCUCUCUCU)producedtwoalternatingaminoacids.This,combinedwiththeNirenbergandLederexperiment,showedthatUCUcodesforSerineandCUCcodesforLeucine.RNAswiththreerepeatingorACUACUACU,orCUACUAproducedthreedifferentstringsofaminoacids.RNAswithfourrepeatingunitsincludingUAG,UAA,orUGA,producedonlydipeptidesandtripeptidesthusrevealingthatUAG,UAAandUGAarestopGeneSincethen,muchresearchhasbeenconductedtomodulatestepsinthegeneexpressionprocess.Thesestepsincludetranscription,RNAsplicing,translation,andpost-translationalmodificationwhichareusedtocontrolthechemicalandstructuralnatureofproteins.[12]MajoreventsinthehistoryofMolecularBiology1952-19601956GeorgeEmilPaladeshowedthesiteofenzymesmanufacturinginthe smismadeonRNAorganellescalledribosomes.GeorgeEmil Moreover,geneticengineeringgivesengineerstheabilitytodirectlymanipulatethegeneticmaterialsoforganismsusing binantDNAtechniques.The binantDNAmoleculewascreatedbyPaulBergin1972whenhecombinedDNAfromthemonkeySV40withthatofthe MajoreventsinthehistoryofMolecularBiology19701970HowardTeminandBaltimoreindependentlyisolatethefirstrestrictionenzymeThismeansthat:DNAcanbecutintoreproduciblepiecesatspecificsitebyrestrictionenzymescalledThepiecescanbelinkedtobacterialvectorsandintroducedintobacterialThisiscalled(genecloningorbinantDNAtechnology)MajoreventsinthehistoryofMolecularBiology1970-19771977PhillipSharpandRichardRobertsdemonstratedthatpre-mRNAisprocessedbytheexcisionofintronsandexonsaresplicedtogether.

Phillip

RichardMajoreventsinthehistoryofMolecularBiology1986-19951986LeroyHood:Developedautomatedsequencing1986HumanGenomeInitiative1995Moderate-resolutionmapsofchromosomes3,11,12,and22wereThesemapsprovidethelocationsof“markers”oneachchromosometomakelocatinggeneseasier

LeroyMajoreventsinthehistoryofMolecularBiology1995-19961995JohnCraigVenter:Firstbacterialgenomessequenced1995AutomatedfluorescentsequencinginstrumentsandroboticoperationsJohnCraig1996Firsteukaryoticgenome-MajoreventsinthehistoryofMolecularMolecularBiology1997-1999Firsthumanchromosome(number22)MolecularBiology2000-2001InternationalHumanGenomeSequencingpublishedthefirstdraftofthesequenceofthehumangenomeMajoreventsinthehistoryofMolecularBiology2003-PresentApril2003HumanGenomeProjectCompletedMousegenomeisApril2004RatgenomeNext-generationsequencing–genomesbeingsequencedbyMainTopicsofMolecular GeneexpressionandStructureandfunctionofbiologicalGenomics,proteomics,What’s FromReductionlismtoHolism:Omicsandsystembiology GenefunctionsandapplicationtoMedicineandSociology(ie.Drugeffectsandtoxicitiesareusuallycausedbymultiplegeneticfactors,betterunderstandingthehumangenomeisMolecularBio-FromReductionism