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1、Whatiscloning?Cloningmeanstheproductionofgeneticallyidenticalanimals.In1995scientistsattheRoslinInstituteinEdinburgh,ScotlandproducedMeganandMorag-twolambsclonedfromasingleembryo.In1996Dollythesheepwasproduced,thefirstexampleofacloneproducednotfromanembryocellbutf
2、romacelltakenfromanadultsheep.Shewasclonedusinganucleartransfertechnique,wherethenucleusfromacelltakenfromthemammaryglandofanadultsheepwasfusedwithanunfertilizedeggfromwhichthenucleushadbeenremoved.277cellswerefusedinthisway,resultingin29viableembryoswhichwereimpl
3、antedintosurrogateBlackfaceewes.OnegavebirthtoDolly.Dollydiedin2003aftersufferingthesignsofprematureageingsuchasarthritisandalivercomplaint.The'production'ofDollyhassparkedacloningfrenzy.1998sawthearrivalofcowsclonedusingthesametechniquethatproducedMeganandMorag1.
4、TheRoslininstituteclonedthefirstpigin20002.IntheUSin2001arhesusmacaquemonkeycalledTetrawascloned3.AlsointheUSin2002aclonedkittenwasreported4inthesameyearasthefirstclonedrabbitsinFrance5.In2003thefirstclonedmule6,horse7andrat8werereported.AnimalwelfareCloninginvolv
5、esmanypossibilitiesfordetrimentaleffectsonanimals.Forexample,clonedlambsandcalvesarefrequentlyabnormallylargeatbirth-somehavebeentwicenormalsize.Onecloningexpertadmittedin1992that"manyclonedcalvesareabnormal".9InAustralia,alamboffivetimesthemeanbirthweightforthebr
6、eedhasbeenrecorded.Inaddition,clonedanimalsareoftenfoundtohavemalformedinternalorgans.10BothoftheseadverseeffectswereseeninthefirstEdinburghexperimentsin1995thatledtoMeganandMorag.Inadditiontodeaththroughmalformedinternalorgans,onelambhadtobedeliveredbycaesareanse
7、ctionbecauseithadgrowntotwiceitsnormalsizeinthewomb,andallbutoneofthefiveclonedlambswereatleast20%largerthantheyshouldhavebeen.Immediatelyafterbirthmanyclonedlambshavebreathingdifficulties,arelethargicandoftenwillnotsuckle.Asaconsequence,perinatalmortalityishigh.M
8、iscarriageratesarealsohigh;thisisthoughttobeatleastinpartbecauseof'largeoffspringsyndrome'.11Cloningtechniquesalsorequireagreatdealofsurgicalinterventio
