Unit-10---It-is-in-the-DNA

Unit10ItisintheDNATEACHER:Goodmorning.Todaywe’lltalkaboutanimportanttopicinbiology--DNAandDNAtesting.CananybodytelluswhatDNAstandsfor?STUDENT1:deoxyribonucleicacid...TEACHER:Right.It’sthemoleculethatcarriesgeneticinformationinalllivingcells.Nowfirst,we’lllookatwhatDNAisandwhenitwasdiscovered.Then,we’lllookatDNAtestingandseveralapplications,orusesoftesting.ThisisanexcitingtopicforbiologistsbecausethemorewelearnaboutDNA,themoreweseehowsciencemaychangeourlives--fromhealthcaretoourrelationships.OK,whatdoesDNAlooklike?STUDENT1:Itlooksliketwostrings,kindofwrappingaroundeachother.TEACHER:Yes,exactly.There’sasimpledrawingofoneinyourbook.Asyoucansee,amoleculeofDNAconsistsoftwostrandsofchemicalcompoundsarrangedinatwistedpattern.Insidethehumancellarechromosomes.TheDNAisorganizedintwenty-threepairsofchromosomesinthecell.Genesarearrangedonthechromosomesandthesecarryfundamentalgeneticinformationlikehaircolor,eyecolor,orcharacteristicsthataren’tasvisible,suchasintelligence,andalotmore.ScientistshavebeenstudyingDNAforalongtime.First,in1860,GregorMendelmadetwoimportantdiscoveries:tinyparticleshecalledgenes,and,thatgenescarryinformationfromcelltocell.Nowthiswasreallythebeginning.Then,in1953,J.D.WatsonandFrancisCrickdiscoveredanddescribedtheDNAstructure.TheirworkwassoimportantthattheyreceivedtheNobelPrizein1962.Forthefirsttime,scientistscouldunderstandexactlyhowDNAtellsthecellswhattodo.ThisgeneratedmoreDNAresearch,andbytheendofthetwentiethcentury,scientistsmadeotherimportantdiscoveries.ProbablythemostimportantworkwastheHumanGenomeProject.ThegoaloftheHumanGenomeProjectwastocompletethefirstreadingofthehumangenome,thecompletesetofhumanDNA.Uh,thiswasahugejob,butaftertenlongyearsinJune,2000,theheadoftheProjectannouncedthattheyhadidentifiedthecompletesetofhumangenes.Uh,thiswasahugedeal.MostpeoplesawthisasthebeginningofawholenewerainDNAresearch.Scientistscouldreadallofthegeneticmessagesinthehumanbody!Thisis,ofcourse,averybriefhistoryofthestudyofDNA.Allright,let’sconsiderDNAtesting.OneimportantuseofDNAtestingistestingidentity,whichisalsocalledDNAfingerprinting.Here’showaDNAfingerprintisdone.Scientiststakeasmallsampleofsomeone’shairorskin,whichcontainDNA.Next,theytreatthesamplewithchemicalsandmakeafilm,likeasmallphotograph.Onthisfilmthereisavisiblepatternofblackbars.Thispatternofblackbarsisuniqueforeachperson.So,aDNAsamplefromyourhairidentifiesyou,it’s,it’slikeyourfingerprint;itidentifiesyouandyouonly.Iseeaquestion.Miguel?STUDENT2:DoestheDNAfromhairorskinorbloodalllookthesame?TEACHER:No,notexactly.TheDNAfromyourhairwilllooklikehairDNAbutitwillbeuniquelyyourDNApattern.It’ssortoflikeallnoseslooklikenoses,right?Butyournoselookslikeyournoseonly.NowIwanttolookattwoapplications,oruses,ofDNAtesting.First,howitcanbeusedbydoctors,andsecond,howitcanbeusedbythepolice.Withinhealth-care,oneimportantuseistoidentifypotentialforhealthproblems.Researchershavefoundsomegeneslinkedtospecificdiseases.Forexample,Huntington’sdiseaseislinkedtoadefectinchromosome4,andAlzheimer’sdiseaseislinkedtoadefectinchromosome19.Ageneticlinkmeansthatdoctorsknowthatifsomeonehasdefectsinthesegenes,they’remorelikelytogetthesehealthproblems;theirpotentialisincreased.Notice,Ididn’tsay“Researchershavefoundthatsomegenedefectscausespecificdiseases.”Thereissimplyalink.AfterdoctorsperformDNAtesting,theycanthendecidethebestwaytousetheinformation.Forexample,theymaygivemedicationtoapatienttopreventadiseasefromeverstarting.Genetictestingcanalsobeusedtodecidewhichmedicinetogivesomeone.Thisiscalledtargetedmedicine.Tome,thisisveryexcitingandpromising.TherearetinydifferencesinDNAfrompersontoperson.Thesedifferencescanaffectwhichpatientswillbehelpedbyadrug,andwhomaybeharmedbyit.Thisis,uh,atremendousadvantage.Itsaveslivesandmoney.Now,let’slookathowDNAtestingisusedbypolice.ThepolicecanuseDNAfingerprintstoidentifyandtracecriminals.Alltheyneedisasmallamount,ortrace,ofbloodorhairfromthecrimescene.IftheDNAsamplesfromthecrimesceneandthesuspectmatch,theresults,atleastintheUnitedStates,canbeusedasevidenceincourt.So,DNAtestingcanbeusedtohelpputsomeoneinprison.Inmuchthesameway,DNAtestingcanbeusedtohelpinnocentpeopleinprison.PeopleinprisoncannowtrytouseDNAtestingforcrimesthathappened,say,tenyearsago.IftheirDNAfingerprintdoesn’tmatchtheDNAfingerprintfromthecrimescene,thiscanhelpthemgetanewtrialandperhapsgetthemoutofprison.Asyoucansee,therearebenefitstoDNAtesting.However,therearealsosomeconcernsthatthistypeofinformationmightbeusedagainstusinthefuture.Nowlet’sconsiderhowDNAtestingcouldbeusedagainstyou.WhatifacompanyyouwantedtoworkforaskedyoutotakeaDNAtest?AndwhatifyourDNAtestshowedthatyouhadagenedefectlinkedtoacertaintypeofcancer?Wouldthecompanydecidenottohireyou?Peoplealsoworryabouthealthinsurance.They’reafraidtheymightnotbeabletogethealthinsuranceiftheirDNAtestshowsthey’reatahigherriskforcertaindiseases.Asaresult,intheUnitedStates,somelawshavebeenpassedtoprotecttheprivacyofmedicalrecords.NowDNAtestinghasotherpossibilitiesthatwewon’tdiscusstoday.Butinanycase,manypeoplethinkaboutthenegativeusesoftesting--t