美国名人 女科学家 巴巴拉·麦克林托克.docx

《美国名人 女科学家 巴巴拉·麦克林托克.docx》由会员分享，可在线阅读，更多相关《美国名人 女科学家 巴巴拉·麦克林托克.docx（4页珍藏版）》请在优知文库上搜索。

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.Thechangescouldnotbeexplainedbyanyknowntheory.So,shedevelopedherowntheory.Shebelievedthemoveablegeneswerenotgenesatall,butgeneticcont