英语四级考试阅读复习指导.docx

英语四级考试阅读复习指导

形成天才的决定因素应该是勤奋。下面是CN人才网为大家整理的2017年英语四级考试阅读复习指导，欢迎参考~2017年英语四级考试阅读复习指导Acontroversyeruptedinthescientificcommunityinearly1998overtheuseofDNA(deoxyribonucleicacid)fingerprintingincriminalinvestigations.DNAfingerprintingwasintroducedin1987asamethodtoidentifyinpidualsbasedonapatternseenintheirDNA,themoleculeofwhichgenesaremade.DNAispresentineverycellofthebodyexceptredbloodcells.DNAfingerprintinghasbeenusedsuccessfullyinvariousways,suchastodeterminepaternitywhereitisnotclearwhothefatherofaparticularchildis.However,itisintheareaofcriminalinvestigationsthatDNAfingerprintinghaspotentiallypowerfulandcontroversialuses.DNAfingerprintingandotherDNAanalysistechniqueshaverevolutionizedcriminalinvestigationsbygivinginvestigatorspowerfulnewtoolsintheattempttotroveguilt,notjustestablishinnocence.Whenusedincriminalinvestigations,aDNAfingerprintpatternfromasuspectiscomparedwithaDNAfingerprintpatternobtainedfromsuchmaterialashairsorbloodfoundatthesceneofacrime.AmatchbetweenthetwoDNAsamplescanbeusedasevidencetoconvictasuspect.Thecontroversyin1998stemmedformareportpublishedinDecember1991bypopulationgeneticistsRichardC.LewontinofHarvardUniversityinCambridge,Mass.,andDanielL.HartlcalledintoquestionthemethodstocalculatehowlikelyitisthatamatchbetweentwoDNAfingerprintsmightoccurbychancealone.Inparticular,theyarguedthatthecurrentmethodcannotproperlydeterminethelikelihoodthattwoDNAsampleswillmatchbecausetheycamefromthesameinpidualratherthansimplyfromtwodifferentinpidualswhoaremembersofthesameethnicgroup.LewontinandHartlcalledforbettersurveysofDNApatternsmethodsareadequate.Inresponsetotheircriticisms,populationgeneticistsRanajitChakrabortyoftheUniversityofTexasinDallasandKennethK.KiddofYaleUniversityinNewHaven,Conn.,arguedthatenoughdataarealreadyavailabletoshowthatthemethodscurrentlybeingusedareadequate.InJanuary1998,however,thefederalBureauofInvestigationandlaboratoriesthatconductDNAtestsannouncedthattheywouldcollectadditionalDNAsamplesformvariousethnicgroupsinanattempttoresolvesom