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时间:2020-07-26
《新编实用英语第四册unit3reading A课件.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、Unit3MaintainingaSharpEyeNewPracticalEnglishShouldWeFearDolly?ToCloneorNottoCloneNewPracticalEnglishUnit3MaintainingaSharpEyeRelatedInformation1IntensiveStudy2Practice3NewPracticalEnglishUnit3RelatedInformationWhatiscloning?ToHumanGenomeProjectresearchers,cloningreferstocopyinggenesandoth
2、erpiecesofchromosomestogenerateenoughidenticalmaterialforfurtherstudy.Twoothertypesofcloningproducecomplete,geneticallyidenticalanimals.Blastomereseparation(sometimescalled“twinning”afterthenaturallyoccurringprocessthatcreatesidenticaltwins)involvessplittingadevelopingembryosoonafterferti
3、lizationoftheeggbyasperm(sexualreproduction)togiverisetotwoormoreembryos.Theresultingorganismsareidenticaltwins(clones)containingDNAfromboththemotherandthefather.NewPracticalEnglishDolly,ontheotherhand,istheresultofanothertypeofcloningthatproducesananimalcarryingtheDNAofonlyoneparent.Usin
4、gsomaticcellnucleartransfer,scientiststransferredgeneticmaterialfromthenucleusofanadultsheep'suddercelltoaneggwhosenucleus,andthusitsgeneticmaterial,hadbeenremoved.(Allcellsthatarenoteggorspermcellsaresomaticcells.)Unit3RelatedInformationNewPracticalEnglishWhyclone?Onegoalofthisandsimilar
5、researchistodevelopefficientwaystoalteranimalsgeneticallyandreproducethemreliably.Alterationshaveincludedaddinggenes(suchasthoseforhumanproteins)tocreatedrug-producinganimalsaswellasinactivatinggenestostudytheeffectsandpossiblycreateanimalmodelsofhumandiseases.Cloningtechnologyalsomaysome
6、daybeusedinhumanstoproducewholeorgansfromsinglecellsortoraiseanimalshavinggeneticallyalteredorganssuitablefortransplantingtohumans.Unit3RelatedInformationNewPracticalEnglishUsingthesametechniquethatproducedDolly,researchershaveclonedanumberoflargeandsmallanimalsincludingsheep,goats,micean
7、dcows.Butscientistsremainuncertainaboutwhethergeneticchangesinthecellsusedtoobtainnucleiwillleadtoadverseeffectsonthehealthoftheclonedanimals.Unit3RelatedInformationNewPracticalEnglishWhatistheHumanGenomeProject?Startedformallyin1990,theWorldHumanGenomeProjectisa13-
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