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1、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.nDarwinbelievedinamixofblendinginheritanceandtheinheritanceofacquir
2、edtraits(pangenesis).Blendinginheritancewouldleadtouniformityacrosspopulationsinonlyafewgenerationsandthuswouldremovevariationfromapopulationonwhichnaturalselectioncouldact.ThisledtoDarwinadoptingsomeLamarckianideasinlatereditionsofOn the Origin of Species andhislaterbiologicalworks.nTheinheritanceo
3、facquiredtraitswasshowntohavelittlebasisinthe1880swhenAugustWeismanncutthetailsoffmanygenerationsofmiceandfoundthattheiroffspringcontinuedtodeveloptails.http:/en.wikipedia.org/wiki/Gregor_MendelGregorMendelwasinspiredbybothhisprofessorsattheUniversityofOlomouc(i.e.FriedrichFranz&JohannKarlNestler)an
4、dhiscolleaguesatthemonastery(e.g.,FranzDiebl)tostudyvariationinplants,andheconductedhisstudyinthemonasterys2hectareexperimentalgarden.Between1856and1863Mendelcultivatedandtestedsome29,000peaplants(i.e.,Pisum sativum).Hisexperimentsledhimtomaketwogeneralizations,theLawofSegregationandtheLawofIndepend
5、entAssortment,whichlaterbecameknownasMendelsLawsofInheritance.WhenMendelspaperwaspublishedin1866inVerhandlungen des naturforschenden Vereins Brnn,itwasseenasessentiallyabouthybridizationratherthaninheritanceandhadlittleimpactandwascitedaboutthreetimesoverthenextthirty-fiveyears.Gregor MendelFather o
6、f geneticsnAftercompletinghisworkwithpeas,Mendelturnedtoexperimentingwithhoneybeestoextendhisworktoanimals.Heproducedahybridstrain,butfailedtogenerateaclearpictureoftheirhereditybecauseofthedifficultiesincontrollingmatingbehaviorsofqueenbees.Healsodescribednovelplantspecies,andthesearedenotedwiththe
7、botanicalauthorabbreviationMendel.nAfterhewaselevatedasabbotin1868,hisscientificworklargelyended,asMendelbecameconsumedwithhisincreasedadministrativeresponsibilities,especiallyadisputewiththecivilgovernmentovertheirattempttoimposespecialtaxesonreligiousinstitutions.nAfterhisdeath,thesucceedingabbotb
8、urnedallpapersinMendelscollection,tomarkanendtothedisputesovertaxation.Gregor MendelFather of geneticsnMendelsworkwasrejectedatfirst,andwasnotwidelyaccepteduntilafterhedied.nBy1900,researchaimedatfindingasuccessfultheoryofdiscontinuousinheritanceratherthanblendinginheritanceledtoindependentduplicati
9、onofhisworkbyHugodeVriesandCarlCorrens,andtherediscoveryofMendelswritingsandlaws.ThoughErichvonTschermakwasoriginallyalsocreditedwithrediscovery,thisisnolongeracceptedbecausehedidnotunderstandMendelslaws.Rediscovery of Mendels worknThesynthesis,producedbetween1936and1947,reflectstheconsensusabouthow
10、evolutionproceeds.Thepreviousdevelopmentofpopulationgenetics,between1918and1932,wasastimulus,asitshowedthatMendeliangeneticswasconsistentwithnaturalselectionandgradualevolution.nThemodernsynthesissolveddifficultiesandconfusionscausedbythespecializationandpoorcommunicationbetweenbiologistsintheearlyy
11、earsofthe20thcentury.AtitsheartwasthequestionofwhetherMendeliangeneticscouldbereconciledwithgradualevolutionbymeansofnaturalselection.Asecondissuewaswhetherthebroad-scalechanges(macroevolution)seenbypalaeontologistscouldbeexplainedbychangesseeninlocalpopulations(microevolution).nThesynthesisincluded
12、evidencefrombiologists,trainedingenetics,whostudiedpopulationsinthefieldandinthelaboratory.Thesynthesisdrewtogetherideasfromseveralbranchesofbiologywhichhadbecomeseparated,particularlygenetics,cytology,systematics,botany,morphology,ecologyandpaleontology.nJulianHuxleyinventedtheterminhisbook,Evoluti
13、on: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:Fr
14、iedrichMiescherdiscoversaweakacidinthenucleiofwhitebloodcellsthattodaywecallDNAn1880-1890:WaltherFlemming,EduardStrasburger,andEdouardvanBenedenelucidatechromosomedistributionduringcelldivisionn1903:WalterSuttonandTheodorBoverihypothesizesthatchromosomes,whichsegregateinaMendelianfashion,areheredita
15、ryunitsn1908:Hardy-Weinberglawderived.n1910:ThomasHuntMorganshowsthatgenesresideonchromosomesn1913:AlfredSturtevantmakesthefirstgeneticmapofachromosome:lineararrangedgenesClassical geneticsn1918:RonaldFisherpublishesTheCorrelationBetweenRelativesontheSuppositionofMendelianInheritancethemodernsynthes
16、isofgeneticsandevolutionarybiologystarts.Theoriginofpopulationgenetics.n1928:FrederickGriffithdiscoversthathereditarymaterialfromdeadbacteriacanbeincorporatedintolivebacterian1941:EdwardLawrieTatumandGeorgeWellsBeadleshowthatgenescodeforproteins;Classical geneticsn1944:AveryetalshowedDNAasthegenetic
17、materialn1948:BarbaraMcClintockdiscoverstransposonsinmaizen1950:ErwinChargaffshowsthattheamountofadenine,A,tendstobeequaltothatofthymine,T;andC=G.n1952:TheHershey-Chaseexperimentprovesthegeneticinformationofphages(andallotherorganisms)tobeDNAn1953:DNAstructureisresolvedtobeadoublehelixbyJamesD.Watso
18、nandFrancisCrickn1958:TheMeselson-StahlexperimentdemonstratesthatDNAissemiconservativelyreplicatedGenetic:the DNA eran1961-1967:Combinedeffortsofscientistscrackthegeneticcode,includingMarshallNirenberg,HarGobindKhorana,SydneyBrenner&FrancisCrickn1964:HowardTeminshowedusingRNAvirusesthatthedirectiono
19、fDNAtoRNAtranscriptioncanbereversedn1970:Restrictionenzymeswerediscoveredinstudiesofabacterium,Haemophilusinfluenzae,enablingscientiststocutandpasteDNAGenetic:the DNA eran1972:WalterFiersandhisteamdeterminedthesequenceofagene:thegeneforbacteriophageMS2coatproteinn1976:WalterFiersandhisteamdeterminet
20、hecompletenucleotide-sequenceofbacteriophageMS2-RNAn1977:DNAissequencedforthefirsttimebyFredSanger,WalterGilbert,andAllanMaxamworkingindependently.Sangerslabsequencetheentiregenomeofbacteriophage-X174.n1983:KaryBanksMullisinventsthepolymerasechainreactionenablingtheeasyamplificationofDNAn1989:Thehum
21、angenethatencodestheCFTRproteinwassequencedbyFrancisCollinsandLap-CheeTsui.Defectsinthisgenecausecysticfibrosis.Genetics:The genomics eran1995:ThegenomeofbacteriumHaemophilus influenzaeisthefirstgenomeofafreelivingorganismtobesequencedn1996:Saccharomyces cerevisiae,ayeastspecies,isthefirsteukaryoteg
22、enomesequencetobereleasedn1998:Thefirstgenomesequenceforamulticellulareukaryote,Caenorhabditis elegans,isreleasedn2001:FirstdraftsequencesofthehumangenomearereleasedsimultaneouslybytheHumanGenomeProjectandCeleraGenomics.n2003(14April):SuccessfulcompletionofHumanGenomeProjectwith99%ofthegenomesequenc
23、edtoa99.99%accuracy.n2012:TheEncyclopediaofDNAElements(ENCODE)projectrevealedthat80%ofhumangenomeisactive.Genetics:The genomics eranThepartofthehumanDNAthathaslongbeenbestunderstoodisaround20,000protein-codinggenes.Thesegenes,however,makeupintotalonlyaround1.5%oftheDNA,andareseparatedfromeachotherby
24、longstretchesofDNAthatdoesnotcodeforproteins.ThisremainingDNAincludestheso-calledregulome,whichcomprisesavarietyofDNAelementsthatinonewayoranothermodulatetheexpressionofprotein-codinggenes.Ithasnotbeenclear,though,howmuchofthetotalDNAiscomprisedwithintheregulome.Untilrecently,themajorityviewhasbeent
25、hatmuchoftheDNAisjunkDNAthatisnevertranscribedandhasnobiologicalfunction.ThecentralgoaloftheENCODEprojectistomapouttheregulome,bydeterminingwhichpartsoftheDNAbelongtoitandthemechanismsbywhichthosepartsinfluencegenetranscription.nTheENCODEConsortiumreportedthattheywereabletoassignbiochemicalfunctions
26、toover80%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(2
27、1),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？