教材试题 unit 2 reading

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1、Unit2CloningPre-readingInpairsdiscusswhatyouunderstandaboutcloning.Thenlistthequestionsyouwanttofindout.Shareyourlistswithoneanother.Questionsaboutcloning1Whatisaclone?2Howisacloneproduced?3Whatbenefitscanhumansgainfromcloning?4Whatproblemsmayarisewhenhumansarecloned?56ReadingCLO

2、NING:WHEREISITLEADINGUS?Cloninghasalwaysbeenwithusandisheretostay.Itisawayofmakinganexactcopyofanotheranimalandplant.Ithappensinplantswhengardenerstakecuttingsfromgrowingplantstomakenewones,orwhensmallpartsofaplantaretakenandgrowninalaboratory.Italsohappensinanimalswhentwinsident

3、icalinsexandappearanceareproducedfromthesameoriginalegg.Thefactisthattheyarenaturalclonesofeachother.Cloninghastwomajoruses.Firstly,gardenersuseitallthetimetoproducecommercialquantitiesofplants.Secondly,itisvaluableforresearchonnewplantspeciesandformedicalresearchonanimals.Clonin

4、gplantsisstraightforwardbutthecloningofanimalsismorecomplicated.Theprocedureisdifficulttoundertake,andatfirstitwasnotaccurateenough.Manyattemptstoclonemammalsfailed.Butatlastthedeterminationandpatienceofthescientistswasrewardedin1996withabreakthrough－thecloningofDollythesheep.The

5、procedureworkslikethis:1FemalesheepAprovidesaneggcell.2Thenucleusisremovedfromtheeggcell.3Theeggcellisreadyforanewnucleus.4FemalesheepBprovidesasomaticcellfortheclone.Thenucleusofthiscellcontainsallthegenesneededtoproduceanewsheep.5Thenucleusistakenoutofthesomaticcell.6Thenucleus

6、fromsheepBandtheeggcellfromsheepAarejoinedusingelectricity.7Thecelldividesandgrowsintoanembryo.8TheembryoisputintofemalesheepC.9ThelambisthecloneofthedonatedcellfromSheepBwhichprovidedthenucleus.Thewholescientificworldfollowedtheprogressofthefirstsuccessfulclone,Dollythesheep.The

7、factthatsheseemedtodevelopnormallywasveryencouraging.ThencamethedisturbingnewsthatDollyhadbecomeseriouslyill.CloningscientistswerecastdowntofindthatDolly’sillnessesweremoreappropriatetoamucholderanimal.Sadlythesamearbitraryfateaffectedotherspecies,suchasclonedmice.Thequestionthat

8、occurredtothescientistswas:“Wouldthisbea