英语第8册第2单元.doc

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1、Unit2CloningSectionⅠWarmingUp&Reading—Pre-reading1．Whataretheadvantagesanddisadvantagesofcloning?2．Notonlyanimalsbotalsoplantscanbecloned．Doyouknowthedifferencebetweenthem?Pleasereadthefollowingpassagetogettheanswer．Anewstudyofplantsthatarereproducedhycloninghasshownwhyclonedplantsarenotldent

2、lcal.Scientistshaveknownorsorfletimethatclonedorganismserenotalwaysidcntical：theirobservablecharacteristicsandtraitscanvary，andthisvariationcanbepassedontotileiicxtgeneration．Thisisdcspirethefactthattheyatederived(获得)fromgenedcallyidenticalfoundercells.Now，ateamfromOxfordUniversity，theUK．andK

3、ingAbdu№hUniversityofScienceandTechnology，SaudiArabia，believetheyhavefoundoutwhythisisthecaseinplants：thegenomes(染色体)ofregenerateplantscarryrelativelyhighfrequenciesofnewDNAsequencemutations(变异)thatwerenotpresentinthegenuineofthedonorplant．Theteamreportedtheirfindingsinthisweek’sCurrentBiolog

4、y.“Wherethesenewmutationsactuallycoomfromisstillamystery，”saidProfessorHarberd.“TheymayariseduringtheregenerationprocessitselforduringthecelldivisionsinthedonorplantthatgaverisetotherootceilsfromwhichtheregenerateplantsarecreatedWeareplanrlingfurtherresearchtofindoutwhichofthesetwoprocessesis

5、responsibleforthesemutations.WhatwecanSaylsthatnaturehassafelybeenemployingwhatyoumightcalla‘cloning’processinplantsfoTmillionsofyears，andthattheremustbcgoodevolutionaryreasollswhythesemutatlonsareintroduced．”Thenewresultssuggestthatvariationinclonesofplantsmayhavediffcrentunderlyingcausesfro

6、mthoseofvariationincloncsofanlmalswhereitisbelievedthattheeffectofenvironmerltalfactorsonhowanimalgenesareexpressedisnloreimportantandnosimilarhighfrequenciesofmutationshavebeenobserved．ProfessorHarberdsaid，“WhileourrcstlltShighlightthatclonedplantsaadanimalsareverydifferent，theymaygiveusinsi

7、ghtsintohowbacterialandcancercellsrcplicatethcmselves，andhowmuutationsariseduringtheseprocesseswhich，ultimately，haveanimpactonhumanhealth．”Step1WarmingUp1．Howmuchdoyouknowaboutclone?Whatisclone?Andwhatarenaturalcloneandman—madeclone?2．Lookatt