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1、美国名人女科学家巴巴拉麦克林托克BarbaraMcCIintockplaystopmutemaxvolume00:00-15:51repeatByGeorgeGrow2005-5-28(THEME)VOICEONE:mDougJohnson.VOICETWO:AndmBarbaraKleinwithPEOPLEINAMERICAinVOASpecialEnglish.Today,wetellaboutBarbaraMcClintock.Shewasoneofthemostimportantscientistsofthetwentiethcentury.Shemadeimportantdisco
2、veriesaboutgenesandchromosomes.(THEME)VOICEONE:BarbaraMcClintockwasborninnineteen-oh-twoinHartford,Connecticut.Barbarawasthethirdoffourchildren.HerfamilymovedtotheBrooklynareaofNewYorkCityinnineteen-oh-eight.Barbarawasanactivechildwithinterestsinsportsandmusic.Shealsodevelopedaninterestinscience.She
3、studiedscienceatCornellUniversityinIthacazNewYork.Barbarawasamongasmallnumberofundergraduatestudentstoreceivetrainingingeneticsinnineteentwenty-one.Yearslater;shenotedthatfewcollegestudentswantedtostudygenetics.VOICETWO:Intheearlynineteen-twentieszgeneticshadnotreceivedwidespreadacceptanceasasubject
4、.Onlytwentyyearshadpassedsincescientistsre-discoveredthetheoriesofheredity.GregorMendelproposedtheseideasaftercompletingaseriesofexperimentswithplants.Hisexperimentshelpedscientistsbetterunderstandhowgenesoperate.Theyshowedhowgeneticqualitiesarepassedtolivingthingsfromtheirancestors.VOICEONE:Barbara
5、McClintockdecidedtostudybotany,thescientificstudyofplants,atCornellUniversity.Shecompletedherundergraduatestudiesinnineteentwenty-three.McClintockdecidedtocontinuehereducationatCornell.Shecompletedamastersdegreeinnineteentwenty-five.Twoyearslateshefinishedallherrequirementsforadoctoratedegree.Inthel
6、atenineteen-twenties,McClintockjoinedseveralotherstudentsinagroupthatstudiedgenetics.ThestudentsincludedafuturewinneroftheNobelPrize,GeorgeBeadle.AnotherwasMarcusRhoades.Yearslater,hewouldbecomealeadingexpertingenetics.McClintocksaidbothmenrecognizedtheimportanceofexploringtheconnectionbetweengenesa
7、ndchromosomes.McClintockstayedatCornellaftershecompletedhereducation.Shetaughtstudentsbotany.Shealsosupervisedgeneticstudiesofthecornplant,ormaize.Shestudiedchromosomes,whicharelinesofgenes.Shemadeseveraldiscoveriesaboutgenesandchromosomes.VOICETWO:Thenineteenthirtieswerenotagoodtimetobeayoungscient
8、istintheUnitedStates.Thecountrywasinthemiddleofthegreateconomicdepression.MillionsofAmericanswereunemployed.Malescientistswereofferedjobs.Butfemalegeneticistswerenotmuchindemand.McClintockreceivedtwoofferstotravelandcarryoutresearchprojects.ThefirstcamefromAmericasNationalResearchCouncil.Sheworkedat
9、severalplaces,includingCornellandtheUniversityofMissouriinColumbia.Later,agroupcalledtheGuggenheimFoundationprovidedfinancialaidforhertostudyinGermany.McClintockwenttoBerlin,butreturnedtoCornellthefollowingyear.Herskillsandworkwerewidelypraised.Butshestillwasunabletofindapermanentjob.(MUSIC)VOICEONE
10、:Foryears,scientistshadbeenusingx-raystostudygeneticmaterialinplantsandotherorganisms.Theyfoundthatx-rayscausedgenestochange.Sometimes,thex-raysphysicallybrokethechromosome.Geneticresearcherslookedforchangesintheorganism.Thentheyusedthisinformationtoproduceamaplinkingthechangestoasingleareaofthechro
11、mosome.McClintockbecameinterestedinthewaygenesreactedtounusualevents.SheformedasuccessfulworkingrelationshipwithLewisStadleroftheUniversityofMissouri.Hehaddemonstratedtheeffectsofx-raysoncorn.StadlersentmaizetreatedwithradiationtoMcClintock.Sheidentifiedunusualareasshecalledringchromosomes.Shebeliev
12、edtheywerechromosomesbrokenbyradiation.Thebrokenendssometimesjoinedtogetherandformedacircle,orring.Thisledhertobelievethatastructureattheendofthechromosomepreventschromosomesfromchanging.Shecalledthisstructurethetelomere.VOICETWO:StadlergottheUniversityofMissouritoofferapermanentpositiontoMcClintock
13、innineteenthirty-six.Shebecameanassistantprofessor.Duringhertimeattheuniversity,sheworkedwithplantstreatedwithx-rays.Shealsodiscoveredplantswithchromosomesthatbrokewithouthelpofradiation.Shedescribedthisactivityasthebreakage-fusion-bridgecycle.Universityofficialsandprofessorsrecognizedtheimportanceo
14、fMcClintocksresearch.Yetshebelievedthatshewasnotabletomakeprogressinherposition.SoshedecidedtoleavetheUniversityofMissouri.(MUSIC)VOICEONE:AnoldfriendfromCornell,MarcusRhoades,invitedMcCIincocktospendthesummerofnineteenforty-oneworkingattheColdSpringHarborLaboratory.ItisaresearchcenteronLongIsland,n
15、earNewYorkCity.McClintockstartedinatemporaryjobwiththegeneticsdepartment.Ashorttimelater,sheacceptedapermanentpositionwiththelaboratory.Thisgaveherthefreedomtocontinueherresearchwithouthavingtoteachorrepeatedlyaskforfinancialaid.AtColdSpringHarborLaboratory,McClintockcontinuedherworkwiththebreakage-
16、fusion-bridgecycle.Shefoundthatsomecornplantgenesactedinanunusualway.Theyappearedtomovefromcelltocellduringdevelopmentofcornparticles,orkernels.Shediscoveredthatthegenesmovedonandbetweenchromosomes.VOICETWO:McClintockconfirmedherdiscoveryandextendedherobservationsforsixyears.Thechangescouldnotbeexpl
17、ainedbyanyknowntheory.So,shedevelopedherowntheory.Shebelievedthemoveablegeneswerenotgenesatall,butgeneticcontrollersorcontrollingelements.Shesaidtheyinfluencedtheactionsofothergenes.Duringthisperiod,McClintockwaselectedtotheNationalAcademyofSciences.Shewasthethirdwomaneversohonored.Shealsowasnamedpr
18、esidentoftheGeneticsSocietyofAmerica.VOICEONE:Innineteenfifty-one,McClintockwasaskedtopresentherfindingsataconferenceheldatColdSpringHarborLaboratory.Herreportdescribedthemovementofgenesfromonepartofachromosometoanother.Sheusedthepresentationtodiscussherideasofcontrollingelementsingenes.Theotherscie
19、ntistsreactedtoherideaswithamixtureofcriticismandsilence.Mostscientistsbelievedthatgenesdidnotmove.Fewpeopleseemedtoacceptherfindings.Yetothersarguedthatherexperimentswerecomplexanddifficulttoexplain,eventootherscientists.Theysaidshewouldnothavebeeninvitedtospeakunlessconferenceorganizersunderstoods
20、omeoftheimportanceofherwork.(MUSIC)VOICETWO:Foryears,manyscientistsdismissedMcClintocksfindings.Duringthisperiod,shecontinueddoingherownworkandreachingherownfindings.Beginninginthelatenineteen-fiftieszshewenttoCentralandSouthAmericatostudydifferentkindsofmaizeplants.Sheexaminedthedevelopmentofagricu
21、lturalmaizebynativepeoples.Shealsoassistedyoungerscientistsandstudentsingenetics.HerworkattheColdSpringHarborLaboratorywasrecognizedinnineteenseventy.ShewasgiventheAmericangovernmentshighestscienceaward-theNationalMedalofScience.VOICEONE:Bythenineteen-seventies,newlydevelopedmethodsofmolecularbiolog
22、yconfirmedwhatMcClintockhadlearnedthroughobservation.Herdiscoverieshavehadaneffectoneverythingfromgeneticengineeringtocancerresearch.McClintockwontheNobelPrizeforPhysiologyorMedicineinnineteeneighty-threeforherdiscoveryoftheabilityofgenestochangepositionsonchromosomes.ShewasthefirstAmericanwomantowi
23、nanunsharedNobelPrize.BarbaraMcClintockremainedatColdSpringHarborfortherestofherlife.Shediedinnineteenninety-two.Shewasninetyyearsold.(THEME)VOICETWO:ThisprogramwaswrittenbyGeorgeGrow.LawanDaviswasourproducer.mBarbaraKlein.VOICEONE:AndmDougJohnson.JoinusagainnextweekforPEOPLEINAMERICAinVOASpecialEnglish.
