英语听力英语高级听力材料The Ghost In Your Genes.docx

英语听力英语高级听力材料The Ghost In Your Genes.docx

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英语听力英语高级听力材料TheGhostInYourGenes

Weareonthebrinkofuncoveringahiddenworld,aworldthatconnectspastandfuturegenerationsinwaysweneverimaginedpossible.

Whatthismeansisanenvironmentalexposurethatyourgrandmotherhadcouldcauseadiseaseinyoueventhoughyou'veneverbeenexposedtothetoxin.Andyouaregonnapassitontoyourgreat-grandkids.

Theseextraordinarydiscoverieshavethepotentialtoaffecteveryaspectofourlives.

It'snotjustthegenes,butalsotheenvironmentintheearlylifeofyourancestors.It'snotsomuchyou'rewhatyoueatassomethingyouarewhatyourmotherate,andmaybeyouarewhatyourgrandmotherate.Andifyoutakeourdata,you'rewhat'sstressyourgrandmotherorgrandfatherhad.

Itwouldchangethewaywethinkaboutourrelationshipwitheverygeneration.

（it）Makesmefeelclosertomychildren.WhatIexperienced,intermsofenvironmentwillhavesometypeoflegacyinmychildrenandmygrandchildren.

Thescienceofinheritanceisbeingturnedonitshead.

We'rechangingtheviewofwhatinheritanceis.

ThissmallSwedishtownmayholdtheevidencetolaunchamedicalrevolution.ÖverkalixlieshuddledontheedgeoftheArcticCircle.Inaccessibleandremote,itwascutofffromtherestoftheworldformostofitshistory.MarcusPembreyhastraveledheretomeethiscolleague,OlovBygren.Theybelievethatthestorylyingburiedinthesegraveyardsmayholdtheprooftotheirradicalideas.

Herewehaveatleast2generations.

Inthesamegrave.

Inthesame...

Thisgroupofpeoplecouldcontributetoreallyaseachangeinthewaywethinkaboutinheritance.

Theyhavecometothischurchyardtofindgrandmothersandgranddaughters,grandfathersandgrandsons,connectingpeoplewholivedalmostahundredyearsapartinentirelynewways,uncoveringlinksthatconfoundscientificthinking.

Uptonow,inheritanceisjustthegenes,theDNAsequence.Isuspectthatwe'regonnabeabletodemonstratethattheinheritanceismorethanthat.

Thisisagrandson,asitwere,inourstudy.

Itistheculminationofmorethantwentyyears'workandforthefirsttime,Pembreyisconfrontingthemagnitudeoftheirdiscovery.

Itreallyhascomealiveforme,comingheremorethanIhadexpected.It'sreallyquiteso,I'm,sureaboutit,wonderful.

MarcusPembreyisoneofaselectbandofscientists,abandofscientistswhoaredaringtochallengeanorthodoxy.Theybelievethelivesofourparents,grandparents,andevenourgreatgrandparentscandirectlyaffectourwell-being,despiteneverexperiencinganyofthesethingsourselves.Tomany,theseideasareregardedasscientificheresy.

Youcannotpredictwhereimportantdiscoverieswillbe.Theonlythingthatyoucandoistofollowyourinstinct.

Conventionalbiologyhasalwaysbelievedthatourgeneticinheritanceissetinstoneatthemomentofourconception.Atthatinstant,weeachreceiveasetofchromosomesfrombothourmotherandfather.Withinthesechromosomesarethegenes,stripsofcodedDNA,thebasicunitofinheritance.Afterconception,itwasassumedthatourgenesarelockedawayinsideeverycellofthebody,protectedanduntouchedbythewayyoulive.Sowhatyoudoinyourlifemayaffectyou,butyourgenesremainuntainted,unchangedforfuturegenerations.Inclassicgenetics,yourparentsandgrandparentssimplypassontheirgenes.Theexperiencestheyaccumulateinalifetimeareneverinherited,lostforeverasthegenespassuntouchedthroughgenerationaftergeneration.

Thebiologyofinheritancewasareassuringlypureprocess,orsoitseemed.Intheearly80s,MarcusPembreyheadedtheclinicalgeneticsdepartmentatGreatOrmondStreetHospitalforChildren.Hewasfrequentlytreatingfamilieswithunusualgeneticconditions.

Wewereconstantlycomingacrossfamilieswhichdidn'tfittherules,didn'tfitanyofthepatternsthatgeneticsweresupposedtofit.Soyouthinkofchromosomeabnormalitiesandyoucheckthechromosomesandtheyarenormal,soyouthenhavetostartimagining,asitwere,youknow,whatmightbeunderlyingthisandyouwerereallydriventotryandworkitoutbecausethefamiliesneededsomehelp.

Themorefamilieshesaw,themoretherulesofinheritanceappearedtobreakdown--diseasesandconditionsthatsimplydidn'tfitwiththetextbookconventions.Oneconditioninparticularcaughthiseye,Angelmansyndrome.

NamedafterHenryAngelman,thepediatricianwhofirstdescribedAngelmansyndrome.Hereferredtothemashappypuppetchildrenbecauseitdescribed,tosomeextent,thefeatures.Theyhavearatherjerkysortofmovementwhentheyarewalking.Thesechildrenhavenospeech.Theyareseverelyincapacitatedintermsoflearning,butareuncharacteristicallyhappyastheyaresmilingallthetime.

Theconditionwascausedbyageneticfault:

akeysequenceofDNAwasmissing,deletedfromChromosome15.

Thenwecameacrossaparadox:

atthesametime,er,thesamechange,thesamelittledeletionofChromosome15hadbeenclearlyassociatedwithaquitedifferentsyndrome,muchmilderintermsof,er,ofintellectualimpairment,thePrader-Willisyndrome.Thesechildrenarecharacterizedbybeingveryfloppyatbirth,butoncetheystartedeatingproperlyandsoon,theythenhadaninsatiableappetiteandwouldgetvery,verylarge.

WhatPembreysawsimplymadenosense.Hereweretwocompletelydifferentdiseases,AngelmansyndromeandPrader-Willisyndromebeingcausedbyexactlythesamegeneticfault.

Soherewe'reinabizarresituationreally,howcouldwehaveproposedthatthesamedeletioncouldcausea,adifferentsyndrome?

ItappearedtoPembreyasifthesimpleviewofinheritancewasbeginningtounravel,buthisdoubtswerecontrarytothetideofoptimismsweepingthescientificcommunity.Intheearly1990s,thebiggestprojecteverundertakeninbiologywascaptivatingtheworld.

TheHumanGenomeProjectwillbeseenastheoutstandingachievementinthehistoryofmankind.

TheHumanGenomeProjectwastobethepinnacleofacenturyofworkongenesandgenetics.Itseemedasifthesecretsoflifewereatourfingertips.

Thegeneticblueprintofmankind...

Nothingelse,merelythewholehumangeneticcodeisasetofinstructionstomakeahumanbeing.

HumangenomeislikeaBiblewhereeverythingwaswrittendown.Thehopeandtheexpectationwasthatoncewehadthatbookinfrontofus,andalltheletterswecouldjustreaddownthepages,andwewouldunderstandhowthebodywasputtogether.

Itwouldofferacompleteunderstandingofhumanbiologyatamolecularlevel.Thehopewasthatoncethecodewaswrittendown,scientistscouldfindthegeneticcauseandcureforeverydisease.

Thelistisendless.

Wewerethinkingofgenesinaverymechanicalway.Wewerethinkingofthemjustintermsofthesequenceoftheletterswhenwewereworkingouthowwecouldworkoutwhatalltheletterswereinthebook.

Scientistsestimatedthatthehumangenome,thebookoflife,wouldcontainaround100,000genes.

Andthenwhentheystartedsequencingthey,theyrealizedtheremaybe100,000genes,anditpoppeddownto60,andthenitpoppeddownto50,Imean,andslowlywentdowntoamuchsmallernumber.Infactwefoundoutthatthehumangenomeisprobablynotascomplexanddoesn'thaveasmanygenesas,asplantsdo.Sothattheymadeusreallyquestionitall.Ifthegenomehaslessgenesinthisspeciesversusthisspecies,andwearemorecomplexpotentially,what'sgoingonhere?

Now,scientistsestimatethereareprobablylessthan30,000genes.

Webelieved,Ibelievednaivelythatwewouldbeabletofindthegeneticcomponentsofcommondiseases.That'sproventobeverydifficult.Theideaofone-gene-one-diseasedoesnotexplainitall.

30,000genesdidn'tappearenoughtoexplainhumancomplexity.Therehadtobesomethingthey'dmissed.ThefirsthintsofwhatwasmissinglayinthecuriousparadoxofthePrader-WilliandAngelmansyndromes,twoquitedifferentdiseasescausedbyexactlythesamegeneticfault.WhenPembreylookedattheinheritancepatternfortheirconditionshenoticedsomethingevenstranger.

WhatreallymatteredwastheoriginoftheChromosome15thathadthedeletion.IfthedeletionwasontheChromosome15thatthechildhadinheritedfromfatherthenyouhadPrader-Willisyndrome.Whereas,ifthe,er,deletion,er,wasinheritedfromthemother,er,youhadtheAngelmansyndrome.

ItwasacompletesurprisethatthesamemissingstripofDNAcouldcauseonediseasewhenitcamefromthemotherandacompletelydifferentdiseasewhenitcamefromthefather.Itwasasifthegenesknewwheretheycamefrom.

You'vegotadevelopingfetusmanifestingthiscondition.HowdoestheChromosome15knowwhereitcamefrom?

It,theremusthavebeenatagoranimprintplacedonthatchromosomeduringeithereggorspermformationinthepreviousgenerationto,tosay"Hi,Icamefrommother,Icamefromfather"andwearefunctioningdifferently.Sothat'sthekeythingthatalthoughtheDNAsequenceisthesamethedifferentsetsofgeneswerebeingsilenceddependingonwhetheritcamefromthemotherorfromthefather.

ItshowedthattherewasclearlymoretoinheritancethansimplythecodedsequenceofDNA.

Wethenrealizedthatweweredealingwithwhatisnowknownasgenomicimprinting.Whatgenomicimprintingmeansis,inanutshell,thatgeneshaveamemoryofwheretheycamefrom.

SomethingotherthanjusttheDNAwascapableofmovingbetweengenerations.Itwasatantalizingglimpseintothisunknownandunexpectedworld.Ahiddenlayeractingonandabletodirectlycontrolhowourgenesfunction.Itmeantthatinheritancewasnotsimplyaboutwhichgenesyouinherited,butwhetherthos