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Unit2Cloning[话题导读]导语：大家对于克隆这一话题并不陌生，但是到底什么是克隆，如何才能够进行克隆等细节性问题对于大部分人来说还是很神秘的。WhatisCloningHaveyoueverwishedyoucouldhaveacloneofyourselftodoyourhomeworkwhileyouwentouttoplaywithyourfriends？Imagineifyoucouldreallydothat,wherewouldyoustart?Whatexactlyiscloning?Cloningisawayofmakinganorganism(有机体)thatisanexactgenetic(基因的)copyofanother.ThismeansthateverysinglebitofDNAisthesamebetweenthetwo!Youmightnotbelieveit,buttherearehumanclonesamongusrightnow.Theyweren'tmadeinalab,though.They'reidentical(同样的)twins,creatednaturally.Below,we'llseehownaturalidenticaltwinsrelatetomoderncloningtechnologies.Howiscloningdone?YoumayhavefirstheardofcloningwhenDollythesheepshoweduponthescenein1997.CloningtechnologieshavebeenaroundformuchlongerthanDolly,though.Howdoesonegoaboutmakinganexactgeneticcopyofanorganism？Thereareacoupleofwaystodothis:artificialembryotwinning(人工胚胎双生)andsomaticcellnucleartransfer(体细胞核移植).Howdotheseprocessesdiffer?1．ArtificialEmbryoTwinningArtificialembryotwinningistherelativelylowtechversionofcloning.Asthenamesuggests,thistechnologymimicsthenaturalprocessofcreatingidenticaltwins.2．SomaticCellNuclearTransferSomaticcellnucleartransfer(SCNT),usesanapproachdifferentfromartificialembryotwinning,butitproducesthesameresult:anexactclone,orageneticcopy,ofanother.ThiswasthemethodusedtocreateDollythesheep.SectionⅠWarmingUp&Prereading&Reading—Comprehending练读文记词汇学翻译1教材助读[先读通]CLONING∶WHEREISITLEADINGUS？Cloninghasalwaysbeenwithusandisheretostay.Itisawayofmakinganexact①copyof②anotheranimalorplant.Ithappensinplantswhengardenerstakecuttings③fromgrowingplantstomakenewones.Italsohappensinanimalswhentwins④identical⑤insexandappearanceareproducedfromthesameoriginalegg.Thefactisthatthesearebothexamplesofnaturalclones⑥.Cloninghastwomajoruses.Firstly，gardenersuseitallthetime⑦toproducecommercial⑧quantitiesof⑨plants.Secondly，itisvaluableforresearchonnewplantspeciesandformedicalresearchonanimals.Cloningplantsisstraightforward⑩while⑪cloninganimalsisverycomplicated⑫.Itisadifficulttasktoundertake⑬.Manyattemptstoclonemammals⑭failed.Butatlast⑮thedeterminationandpatienceofthescientistspaidoff⑯in1996withabreakthrough⑰—thecloningofDollythesheep.Theprocedure⑱workslikethis：1FemalesheepAprovidesaneggcell.2Thenucleus⑲isremovedfrom⑳theeggcell.3Theeggcellisreadyforanewnucleus.4FemalesheepBprovidesasomatic○21cellfortheclone.Thenucleusofthiscellcontainsallthegenesneededtoproduceanewsheep○22.5Thenucleusistakenoutofthesomaticcell.6ThenucleusfromsheepBandtheeggcellfromsheepAarejoinedusingelectricity○23.7Thecelldividesandgrowsintoanembryo○24.8TheembryoisputintofemalesheepC,whobecomesthecarrier○25oftheclone○26.9Thelambisthecloneofthedonated○27cellfromSheepBwhichprovidedthenucleus○28.Ontheonehand○29，thewholescientificworldfollowedtheprogressofthefirstsuccessfulclone,Dollythesheep.Thefactthatsheseemedtodevelopnormally○30wasveryencouraging.ThencamethedisturbingnewsthatDollyhadbecomeseriouslyill○31.Cloningscientistswerecastdown○32tofindthatDolly'sillnessesweremoreappropriateto○33amucholderanimal.Altogether○34Dollylivedsixandahalfyears,halfthelengthofthelifeoftheoriginalsheep.Sadlythesamearbitrary○35fate○36affectedotherspecies,suchasclonedmice.Thequestionsthatconcernedallscientists○37were：“Wouldthisbeamajordifficultyforallclonedanimals?Wouldithappenforever?Coulditbesolvedifcorrections○38weremadeintheirresearchprocedure？”Ontheotherhand,Dolly'sappearanceraisedastormof○39objections○40andhadagreatimpact○41onthemedia○42andpublicimagination.Itbecamecontroversial○43.Itsuddenlyopenedeverybody'seyestothepossibilityofusingcloningtocureseriousillnessesandeventoproducehumanbeings○44.Althoughatpresenthumaneggcellsandembryosneededforcloningresearch○45aredifficulttoobtain○46，newspaperswroteof○47evilleadershopingtoclonethemselvestoattain○48theirambitions○49.Religiousleadersalsoraisedmoral○50questions.Governmentsbecamenervousandmoreconservative○51.Somebegantoreformtheirlegalsystemsandforbade○52researchintohumancloning,butothercountrieslikeChinaandtheUK,continuedtoaccumulate○53evidenceoftheabundantmedicalaidthatcloningcouldprovide○54.However,scientistsstillwonderwhethercloningwillhelporharmusandwhereitisleadingus○55.[再记住]①exact/Iɡ'zækt/adj.精确的；准确的②makeacopyof(＝copy)复制ofmaking...作way的定语。③cutting/'kʌtIŋ/n.剪枝；剪报；剪纸④twin/twIn/n.双胞胎之一；孪生儿之一adj.成对的；成双的⑤identical/aI'dentIkl/adj.同一的；一模一样的⑥Thefactisthat...中，that引导表语从句。⑦allthetime一直⑧commercial/kə'mɜːʃl/adj.商业的；贸易的⑨quantitiesof“大量的”；修饰可数名词复数或不可数名词。⑩straightforward/'streIt'fɔːwəd/adj.简单的；直接的；坦率的⑪while在此表示“而，却”，是并列连词，表示对比关系。⑫complicated/'kɒmplIkeItId/adj.复杂的；难懂的⑬undertake/'ʌndə'teIk/vt.(undertook,undertaken)着手；从事；承担不定式短语toundertake作定语，修饰task。⑭不定式短语toclonemammals作定语，修饰attempts。⑮Firstly...Secondly...atlast...“首先……其次……最后……”，表示论述顺序。⑯payoff得到好结果；取得成功；偿清⑰breakthrough/'breIkθruː/n.突破⑱procedure/prə'siːdʒə/n.程序；步骤；手续⑲nucleus/'njuːklIəs/n.原子核；中心⑳remove...from...将……从……移走○21somatic/səʊ'mætIk/adj.躯体的；肉体的；细胞体的○22过去分词短语neededto...作定语，修饰genes。○23现在分词短语usingelectricity作方式状语。○24embryo/'embrIəʊ/n.胚；胚胎；萌芽时期○25carrier/'kærIə/n.携带者；搬运工；运输工具○26who引导非限制性定语从句，修饰先行词female