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1、精品文档雅思考试阅读模拟试题精选八1.Washing,brushingandvarnishingfossils—allstandardconservationtreatmentsusedbymanyfossilhuntersandmuseumcuratorsalike—vastlyreducesthechancesofrecoveringancientDNA.2.Instead,excavatorsshouldbehandlingatleastsomeoftheirbountywithgloves,andfreezingsamplesastheyarefound,dirtandall,conc
2、ludesapaperintheProceedingsoftheNationalAcademyofSciencestoday.3.AlthoughmanypalaeontologistsknowanecdotallythatthisisthebestwaytouptheoddsofextractinggoodDNA,Eva-MariaGeigloftheJacquesMonodInstituteinParis,France,andhercolleagueshavenowshownjusthowimportantconservationpracticescanbe.Thisinformation
3、,theysay,needstobehammeredhomeamongthepeoplewhoareactuallyoutinthefielddiggingupbones.4.Geiglandhercolleagueslookedat3,200-year-oldfossilbonesbelongingtoasingleindividualofanextinctcattlespecies,calledanaurochs.ThefossilsweredugupatasiteinFrance2016全新精品资料-全新公文范文-全程指导写作–独家原创10/10精品文档attwodifferenttim
4、es—eitherin1947,andstoredinamuseumcollection,orin2004,andconservedinsterileconditionsat-20oC.5.Theteam’sattemptstoextractDNAfromthe1947bonesallfailed.Thenewlyexcavatedfossils,however,allyieldedDNA.6.Becausetheboneshadbeenburiedforthesameamountoftime,andinthesameconditions,theconservationmethodhadtob
5、etoblamesaysGeigl.“AsmuchDNAwasdegradedinthese57yearsasinthe3,200yearsbefore,”shesays.Washin,washout7.Becausemanypalaeontologistsbasetheirworkontheshapeoffossilsalone,theirmethodsofconservationarenotdesignedtopreserveDNA,Geiglexplains.8.Thebiggestproblemishowtheyarecleaned.Fossilsareoftenwashedtoget
6、heron-siteinalargebath,whichcanallowwa上一篇英语：雅思考试阅读模拟试题精选九下一篇英语：2016全新精品资料-全新公文范文-全程指导写作–独家原创10/10精品文档没有了查看更多关于雅思真题的文章网友同时还浏览了：雅思考试阅读模拟试题精选九雅思阅读真题预测雅思阅读全真模拟试题一雅思阅读全真模拟试题二雅思阅读全真模拟试题三雅思阅读全真模拟试题四ter—andcontaminantsintheformofcontemporaryDNA—topermeateintotheporousbones.“NotonlyistheauthenticDNAgettingwa
7、shedout,butcontaminationisgettingwashedin,”saysGeigl.9.MostancientDNAspecialistsknowthisalready,saysHendrikPoinar,anevolutionarygeneticistatMcMasterUniversityinOntario,Canada.Butthatdoesn’tmeanthatbes
