新编英语教程 4 Unit 13 拓展知识.ppt
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新编英语教程 4 Unit 13 拓展知识.ppt

新编英语教程4Unit13拓展知识.ppt

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Furtherdevelopment2.HOWSCIENTISTSCLONECELLSB.BlastocystDivisionInblastocystdivision,scientistsallowafertilizedeggtodivideuntilitformsamassofabout32to150cells,knownasablastocyst.Scientiststhensplittheblastocystintwoandimplantthetwohalvesintotheuterusofasurrogatemother.Thetwohalvesdevelopasidenticaltwins.C.SomaticCellNuclearTransferWhileblastomereseparationandblastocystdivisionproduceanimalscontainingthegeneticmaterialfrombothamotherandfather,somaticcellnucleartransferproducesananimalcarryingthegeneticmaterialofonlyoneparent.Inthistechnique,scientiststransferthegeneticmaterialfromadonor’ssomaticcell(anybodycellotherthananeggorspermcell)toanenucleatedeggcell—thatis,aneggcellwithitsnucleus,andthusitsgeneticmaterial,removed.Theresultingclonedcellcontainsthegeneticmaterialofthedonor’ssomaticcell.GeneticEngineeringFirstClonedCatIdenticalCalves