六章节遗传和遗传物质.ppt

六章节遗传和遗传物质 Still waters run deep.流静水深流静水深,人静心深人静心深 Where there is life,there is hope。有生命必有希望。有生命必有希望Charles DarwinnWhenCharlesDarwinproposedhistheoryofevolutionin1859,oneofitsmajorproblemswasthelackofanunderlyingmechanismforheredity.nDarwinbelievedinamixofblendinginheritanceandtheinheritanceofacquiredtraits(pangenesis).Blendinginheritancewouldleadtouniformityacrosspopulationsinonlyafewgenerationsandthuswouldremovevariationfromapopulationonwhichnaturalselectioncouldact.ThisledtoDarwinadoptingsomeLamarckianideasinlatereditionsofOn the Origin of Species andhislaterbiologicalworks.nTheinheritanceofacquiredtraitswasshowntohavelittlebasisinthe1880swhenAugustWeismanncutthetailsoffmanygenerationsofmiceandfoundthattheiroffspringcontinuedtodeveloptails.http:/en.wikipedia.org/wiki/Gregor_MendelGregorMendelwasinspiredbybothhisprofessorsattheUniversityofOlomouc(i.e.FriedrichFranz&JohannKarlNestler)andhiscolleaguesatthemonastery(e.g.,FranzDiebl)tostudyvariationinplants,andheconductedhisstudyinthemonasterys2hectareexperimentalgarden.Between1856and1863Mendelcultivatedandtestedsome29,000peaplants(i.e.,Pisum sativum).Hisexperimentsledhimtomaketwogeneralizations,theLawofSegregationandtheLawofIndependentAssortment,whichlaterbecameknownasMendelsLawsofInheritance.WhenMendelspaperwaspublishedin1866inVerhandlungen des naturforschenden Vereins Brnn,itwasseenasessentiallyabouthybridizationratherthaninheritanceandhadlittleimpactandwascitedaboutthreetimesoverthenextthirty-fiveyears.Gregor MendelFather of geneticsnAftercompletinghisworkwithpeas,Mendelturnedtoexperimentingwithhoneybeestoextendhisworktoanimals.Heproducedahybridstrain,butfailedtogenerateaclearpictureoftheirhereditybecauseofthedifficultiesincontrollingmatingbehaviorsofqueenbees.Healsodescribednovelplantspecies,andthesearedenotedwiththebotanicalauthorabbreviationMendel.nAfterhewaselevatedasabbotin1868,hisscientificworklargelyended,asMendelbecameconsumedwithhisincreasedadministrativeresponsibilities,especiallyadisputewiththecivilgovernmentovertheirattempttoimposespecialtaxesonreligiousinstitutions.nAfterhisdeath,thesucceedingabbotburnedallpapersinMendelscollection,tomarkanendtothedisputesovertaxation.Gregor MendelFather of geneticsnMendelsworkwasrejectedatfirst,andwasnotwidelyaccepteduntilafterhedied.nBy1900,researchaimedatfindingasuccessfultheoryofdiscontinuousinheritanceratherthanblendinginheritanceledtoindependentduplicationofhisworkbyHugodeVriesandCarlCorrens,andtherediscoveryofMendelswritingsandlaws.ThoughErichvonTschermakwasoriginallyalsocreditedwithrediscovery,thisisnolongeracceptedbecausehedidnotunderstandMendelslaws.Rediscovery of Mendels worknThesynthesis,producedbetween1936and1947,reflectstheconsensusabouthowevolutionproceeds.Thepreviousdevelopmentofpopulationgenetics,between1918and1932,wasastimulus,asitshowedthatMendeliangeneticswasconsistentwithnaturalselectionandgradualevolution.nThemodernsynthesissolveddifficultiesandconfusionscausedbythespecializationandpoorcommunicationbetweenbiologistsintheearlyyearsofthe20thcentury.AtitsheartwasthequestionofwhetherMendeliangeneticscouldbereconciledwithgradualevolutionbymeansofnaturalselection.Asecondissuewaswhetherthebroad-scalechanges(macroevolution)seenbypalaeontologistscouldbeexplainedbychangesseeninlocalpopulations(microevolution).nThesynthesisincludedevidencefrombiologists,trainedingenetics,whostudiedpopulationsinthefieldandinthelaboratory.Thesynthesisdrewtogetherideasfromseveralbranchesofbiologywhichhadbecomeseparated,particularlygenetics,cytology,systematics,botany,morphology,ecologyandpaleontology.nJulianHuxleyinventedtheterminhisbook,Evolution:The Modern Synthesis(1942).OthermajorfiguresincludeR.A.Fisher,TheodosiusDobzhansky,J.B.S.Haldane,SewallWright,E.B.Ford,ErnstMayr,BernhardRensch,SergeiChetverikov,GeorgeGaylordSimpson,andG.LedyardStebbins.Modern evolutionary synthesisn1865:GregorMendelspaper,ExperimentsonPlantHybridizationn1869:FriedrichMiescherdiscoversaweakacidinthenucleiofwhitebloodcellsthattodaywecallDNAn1880-1890:WaltherFlemming,EduardStrasburger,andEdouardvanBenedenelucidatechromosomedistributionduringcelldivisionn1903:WalterSuttonandTheodorBoverihypothesizesthatchromosomes,whichsegregateinaMendelianfashion,arehereditaryunitsn1908:Hardy-Weinberglawderived.n1910:ThomasHuntMorganshowsthatgenesresideonchromosomesn1913:AlfredSturtevantmakesthefirstgeneticmapofachromosome:lineararrangedgenesClassical geneticsn1918:RonaldFisherpublishesTheCorrelationBetweenRelativesontheSuppositionofMendelianInheritancethemodernsynthesisofgeneticsandevolutionarybiologystarts.Theoriginofpopulationgenetics.n1928:FrederickGriffithdiscoversthathereditarymaterialfromdeadbacteriacanbeincorporatedintolivebacterian1941:EdwardLawrieTatumandGeorgeWellsBeadleshowthatgenescodeforproteins;Classical geneticsn1944:AveryetalshowedDNAasthegeneticmaterialn1948:BarbaraMcClintockdiscoverstransposonsinmaizen1950:ErwinChargaffshowsthattheamountofadenine,A,tendstobeequaltothatofthymine,T;andC=G.n1952:TheHershey-Chaseexperimentprovesthegeneticinformationofphages(andallotherorganisms)tobeDNAn1953:DNAstructureisresolvedtobeadoublehelixbyJamesD.WatsonandFrancisCrickn1958:TheMeselson-StahlexperimentdemonstratesthatDNAissemiconservativelyreplicatedGenetic:the DNA eran1961-1967:Combinedeffortsofscientistscrackthegeneticcode,includingMarshallNirenberg,HarGobindKhorana,SydneyBrenner&FrancisCrickn1964:HowardTeminshowedusingRNAvirusesthatthedirectionofDNAtoRNAtranscriptioncanbereversedn1970:Restrictionenzymeswerediscoveredinstudiesofabacterium,Haemophilusinfluenzae,enablingscientiststocutandpasteDNAGenetic:the DNA eran1972:WalterFiersandhisteamdeterminedthesequenceofagene:thegeneforbacteriophageMS2coatproteinn1976:WalterFiersandhisteamdeterminethecompletenucleotide-sequenceofbacteriophageMS2-RNAn1977:DNAissequencedforthefirsttimebyFredSanger,WalterGilbert,andAllanMaxamworkingindependently.Sangerslabsequencetheentiregenomeofbacteriophage-X174.n1983:KaryBanksMullisinventsthepolymerasechainreactionenablingtheeasyamplificationofDNAn1989:ThehumangenethatencodestheCFTRproteinwassequencedbyFrancisCollinsandLap-CheeTsui.Defectsinthisgenecausecysticfibrosis.Genetics:The genomics eran1995:ThegenomeofbacteriumHaemophilus influenzaeisthefirstgenomeofafreelivingorganismtobesequencedn1996:Saccharomyces cerevisiae,ayeastspecies,isthefirsteukaryotegenomesequencetobereleasedn1998:Thefirstgenomesequenceforamulticellulareukaryote,Caenorhabditis elegans,isreleasedn2001:FirstdraftsequencesofthehumangenomearereleasedsimultaneouslybytheHumanGenomeProjectandCeleraGenomics.n2003(14April):SuccessfulcompletionofHumanGenomeProjectwith99%ofthegenomesequencedtoa99.99%accuracy.n2012:TheEncyclopediaofDNAElements(ENCODE)projectrevealedthat80%ofhumangenomeisactive.Genetics:The genomics eranThepartofthehumanDNAthathaslongbeenbestunderstoodisaround20,000protein-codinggenes.Thesegenes,however,makeupintotalonlyaround1.5%oftheDNA,andareseparatedfromeachotherbylongstretchesofDNAthatdoesnotcodeforproteins.ThisremainingDNAincludestheso-calledregulome,whichcomprisesavarietyofDNAelementsthatinonewayoranothermodulatetheexpressionofprotein-codinggenes.Ithasnotbeenclear,though,howmuchofthetotalDNAiscomprisedwithintheregulome.Untilrecently,themajorityviewhasbeenthatmuchoftheDNAisjunkDNAthatisnevertranscribedandhasnobiologicalfunction.ThecentralgoaloftheENCODEprojectistomapouttheregulome,bydeterminingwhichpartsoftheDNAbelongtoitandthemechanismsbywhichthosepartsinfluencegenetranscription.nTheENCODEConsortiumreportedthattheywereabletoassignbiochemicalfunctionstoover80%ofthegenome.MuchofthiswasfoundtobeinvolvedincontrollingtheexpressionlevelsofcodingDNA,whichmakesuplessthan1%ofthegenome.细胞核中的细胞核中的DNA都有用吗？都有用吗？n我们细胞核中的DNA都有用吗？上：历史回顾n我们细胞核中的DNA都有用吗？中：人类基因组测序和ENCODE项目n我们细胞核中的DNA都有用吗？下：任重道远nEddy,S.R.(2012)TheC-valueparadox,junkDNAandENCODE.CurrentBiology,22(21),R898.preprintPDFnNiu,D.K.,andJiang,L.(2012)CanENCODEtellushowmuchjunkDNAwecarryinourgenome?.Biochemicalandbiophysicalresearchcommunications430:1340-1343.doi:10.1016/j.bbrc.2012.12.074nGraur,D.,Zheng,Y.,Price,N.,Azevedo,R.B.,Zufall,R.A.,andElhaik,E.(2013)Ontheimmortalityoftelevisionsets:functioninthehumangenomeaccordingtotheevolution-freegospelofENCODE.GenomeBiologyandEvolutiondoi:10.1093/gbe/evt028nDoolittle,W.F.(2013)IsjunkDNAbunk?AcritiqueofENCODE.Proc.Natl.Acad.Sci.USAdoi:10.1073/pnas.1221376110细胞核中的细胞核中的DNA都有用吗？都有用吗？