遗传和遗传物质专家讲座

VerhandlungendesnaturforschendenVereinsBrünn,

itwasseenasessentiallyabouthybridizationratherthaninheritanceandhadlittleimpactandwascitedaboutthreetimesoverthenextthirty-fiveyears.

GregorMendelFatherofgeneticsAftercompletinghisworkwithpeas,Mendelturnedtoexperimentingwithhoneybeestoextendhisworktoanimals.Heproducedahybridstrain,butfailedtogenerateaclearpictureoftheirhereditybecauseofthedifficultiesincontrollingmatingbehaviorsofqueenbees.Healsodescribednovelplantspecies,andthesearedenotedwiththebotanicalauthorabbreviation"Mendel".Afterhewaselevatedasabbotin1868,hisscientificworklargelyended,asMendelbecameconsumedwithhisincreasedadministrativeresponsibilities,especiallyadisputewiththecivilgovernmentovertheirattempttoimposespecialtaxesonreligiousinstitutions.Afterhisdeath,thesucceedingabbotburnedallpapersinMendel'scollection,tomarkanendtothedisputesovertaxation.GregorMendelFatherofgeneticsMendel'sworkwasrejectedatfirst,andwasnotwidelyaccepteduntilafterhedied.By1900,researchaimedatfindingasuccessfultheoryofdiscontinuousinheritanceratherthanblendinginheritanceledtoindependentduplicationofhisworkbyHugodeVriesandCarlCorrens,andtherediscoveryofMendel'swritingsandlaws.ThoughErichvonTschermakwasoriginallyalsocreditedwithrediscovery,thisisnolongeracceptedbecausehedidnotunderstandMendel'slaws.RediscoveryofMendel'sworkThesynthesis,producedbetween1936and1947,reflectstheconsensusabouthowevolutionproceeds.

Thepreviousdevelopmentofpopulationgenetics,between1918and1932,wasastimulus,asitshowedthat

Mendeliangenetics

wasconsistentwith

naturalselectionandgradualevolution.Themodernsynthesissolveddifficultiesandconfusionscausedbythespecializationandpoorcommunicationbetweenbiologistsintheearlyyearsofthe20thcentury.AtitsheartwasthequestionofwhetherMendeliangeneticscouldbereconciledwithgradualevolutionbymeansofnaturalselection.Asecondissuewaswhetherthebroad-scalechanges(macroevolution)seenbypalaeontologistscouldbeexplainedbychangesseeninlocalpopulations(microevolution).Thesynthesisincludedevidencefrombiologists,trainedingenetics,whostudiedpopulationsinthefieldandinthelaboratory.Thesynthesisdrewtogetherideasfromseveralbranchesofbiologywhichhadbecomeseparated,particularly

genetics,

cytology,

systematics,

botany,

morphology,

ecology

and

paleontology.JulianHuxley

inventedtheterminhisbook,

Evolution:TheModernSynthesis

(1942).Othermajorfiguresinclude

R.A.Fisher,

TheodosiusDobzhansky,

J.B.S.Haldane,

SewallWright,

E.B.Ford,

ErnstMayr,

BernhardRensch,

SergeiChetverikov,

GeorgeGaylordSimpson,and

G.LedyardStebbins.Modernevolutionarysynthesis1865:GregorMendel'spaper,ExperimentsonPlantHybridization1869:FriedrichMiescherdiscoversaweakacidinthenucleiofwhitebloodcellsthattodaywecallDNA1880-1890:WaltherFlemming,EduardStrasburger,andEdouardvanBenedenelucidatechromosomedistributionduringcelldivision1903:WalterSuttonandTheodorBoverihypothesizesthatchromosomes,whichsegregateinaMendelianfashion,arehereditaryunits1908:Hardy-Weinberglawderived.1910:ThomasHuntMorganshowsthatgenesresideonchromosomes1913:AlfredSturtevantmakesthefirstgeneticmapofachromosome:lineararrangedgenesClassicalgenetics1918:RonaldFisherpublishes"TheCorrelationBetweenRelativesontheSuppositionofMendelianInheritance"themodernsynthesisofgeneticsandevolutionarybiologystarts.Theoriginofpopulationgenetics.1928:FrederickGriffithdiscoversthathereditarymaterialfromdeadbacteriacanbeincorporatedintolivebacteria1941:EdwardLawrieTatumandGeorgeWellsBeadleshowthatgenescodeforproteins;Classicalgenetics1944:AveryetalshowedDNAasthegeneticmaterial1948:BarbaraMcClintockdiscoverstransposonsinmaize1950:ErwinChargaffshowsthattheamountofadenine,A,tendstobeequaltothatofthymine,T;andC=G.1952:TheHershey-Chaseexperimentprovesthegeneticinformationofphages(andallotherorganisms)tobeDNA1953:DNAstructureisresolvedtobeadoublehelixbyJamesD.WatsonandFrancisCrick1958:TheMeselson-StahlexperimentdemonstratesthatDNAissemiconservativelyreplicatedGenetic:theDNAera1961-1967:Combinedeffortsofscientists"crack"thegeneticcode,includingMarshallNirenberg,HarGobindKhorana,SydneyBrenner&FrancisCrick1964:HowardTeminshowedusingRNAvirusesthatthedirectionofDNAtoRNAtranscriptioncanbereversed1970:Restrictionenzymeswerediscoveredinstudiesofabacterium,Haemophilusinfluenzae,enablingscientiststocutandpasteDNAGenetic:theDNAera1972:WalterFiersandhisteamdeterminedthesequenceofagene:thegeneforbacteriophageMS2coatprotein1976:WalterFiersandhisteamdeterminethecompletenucleotide-sequenceofbacteriophageMS2-RNA1977:DNAissequencedforthefirsttimebyFredSanger,WalterGilbert,andAllanMaxamworkingindependently.Sanger'slabsequencetheentiregenomeofbacteriophageΦ-X174.1983:KaryBanksMullisinventsthepolymerasechainreactionenablingtheeasyamplificationofDNA1989:ThehumangenethatencodestheCFTRproteinwassequencedbyFrancisCollinsandLap-CheeTsui.Defectsinthisgenecausecysticfibrosis.Genetics:Thegenomicsera1995:ThegenomeofbacteriumHaemophilusinfluenzaeisthefirstgenomeofafreelivingorganismtobesequenced1996:Saccharomycescerevisiae,ayeastspecies,isthefirsteukaryotegenomesequencetobereleased1998:Thefirstgenomesequenceforamulticellulareukaryote,Caenorhabditiselegans,isreleased2023:FirstdraftsequencesofthehumangenomearereleasedsimultaneouslybytheHumanGenomeProjectandCeleraGenomics.2023(14April):SuccessfulcompletionofHumanGenomeProjectwith99%ofthegenomesequencedtoa99.99%accuracy.2023:TheEncyclopediaofDNAElements(ENCODE)projectrevealedthat>80%ofhumangenomeisactive.Genetics:ThegenomicseraThepartofthehumanDNAthathaslongbeenbestunderstoodisaround20,000protein-codinggenes.Thesegenes,however,makeupintotalonlyaround1.5%oftheDNA,andareseparatedfromeachotherbylongstretchesofDNAthatdoesnotcodeforproteins.ThisremainingDNAincludestheso-calledregulome,whichcomprisesavarietyofDNAelementsthatinonewayoranothermodulatetheexpressionofprotein-codinggenes.Ithasnotbeenclear,though,howmuchofthetotalDNAiscomprisedwithintheregulome.Untilrecently,themajorityviewhasbeenthatmuchoftheDNAis"junk"—DNAthatisnevertranscribedandhasnobiologicalfunction.ThecentralgoaloftheENCODEprojectistomapouttheregulome,bydeterminingwhichpartsoftheDNAbelongtoitandthemechanismsbywhichthosepartsinfluencegenetranscription.TheENCODEConsortiumreportedthattheywereabletoassignb