全国专四英语阅读考试特别训练题.docx

全国专四英语阅读考试特别训练题

全国专四英语阅读考试特别训练题 Thinktwicebeforeacting.以下是小编为大家搜索整理的全国专四英语阅读考试特别训练题，希望能给大家带来帮助!更多精彩内容请及时关注我们应届毕业生考试网! Acontroversyeruptedinthescientificcommunityinearly1998overtheuseofDNA(deoxyribonucleicacid)fingerprintingincriminalinvestigations.DNAfingerprintingwasintroducedin1987asamethodtoidentifyindividualsbasedonapatternseenintheirDNA,themoleculeofwhichgenesaremade.DNAispresentineverycellofthebodyexceptredbloodcells.DNAfingerprintinghasbeenusedsuccessfullyinvariousways,suchastodeterminepaternitywhereitisnotclearwhothefatherofaparticularchildis.However,itisintheareaofcriminalinvestigationsthatDNAfingerprintinghaspotentiallypowerfulandcontroversialuses. DNAfingerprintingandotherDNAanalysistechniqueshaverevolutionizedcriminalinvestigationsbygivinginvestigatorspowerfulnewtoolsintheattempttotroveguilt,notjustestablishinnocence.Whenusedincriminalinvestigations,aDNAfingerprintpatternfromasuspectiscomparedwithaDNAfingerprintpatternobtainedfromsuchmaterialashairsorbloodfoundatthesceneofacrime.AmatchbetweenthetwoDNAsamplescanbeusedasevidencetoconvictasuspect. Thecontroversyin1998stemmedformareportpublishedinDecember1991bypopulationgeneticistsRichardC.LewontinofHarvardUniversityinCambridge,Mass.,andDanielL.HartlcalledintoquestionthemethodstocalculatehowlikelyitisthatamatchbetweentwoDNAfingerprintsmightoccurbychancealone.Inparticular,theyarguedthatthecurrentmethodcannotproperlydeterminethelikelihoodthattwoDNAsampleswillmatchbecausetheycamefromthesameindividualratherthansimplyfromtwodifferentindividualswhoaremembersofthesameethnicgroup.LewontinandHartlcalledforbettersurveysofDNApatternsmethodsareadequate. Inresponsetotheircriticisms,populationgeneticistsRanajitChakrabortyoftheUniversityofTexasinDallasandKennethK.KiddofYaleUniversityinNewHaven,Conn.,arguedthatenoughdataarealreadyavailabletoshowthatthemethodscurrentlybeingusedareadequate.InJanuary1998,however,thefederalBureauofInvestigationandlaboratoriesthatconductDNAtestsannouncedthattheywouldcollectadditionalDNAsamples