carolina-labsheets-gene-interaction-with-drosophila

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1、CarolinaLabSheetsTMGeneInteractionwithDrosophilaInintroductorygeneticsstudentscommonlystudytheinfluenceofonegeneononephenotype.Thisislogicalsincestudentsmustunderstandthesimplestcasesbeforetacklingthemorecomplicatedcases.However,studentscaneasilyjumptotheconclusi

2、onthatonegene=onephenotype.Inreality,therearefew,ifany,instancesinwhichthisistrue.EyecolorinDrosophilaisaclassiccase.Acommonintroductoryactivityistohavestudentscrosswild-typeflieswithflieshavingsepiaeyesandstudytheF1andF2ofthatcross.Thestudentsthenconcludethatsep

3、iaisrecessivetothewild-typeallele.ThisistruebutthereisnosinglegeneforeyecolorinDrosophila.Thebrick-redeyecolorofwild-typefliesisproducedbyamixtureofpigments,eachpigmentistheendproductofaseriesofreactions,eachreactionismediatedbyanenzyme,andeachenzymeisaproteintha

4、tresultsfromthetranscriptionofaDNAgene.Alargenumberofgenes,perhaps100,areinvolvedinproducingeyecolorinDrosophila.Thisactivityintroducesstudentstotheconceptofinteractinggenesthroughadihybridcrossinvolvingthebrownlocus(bw)onchromosome2andscarletlocus(st)onchromosom

5、e3.Brownpigmentsareproducedthroughtheommochromepathway,andbright-redpigmentsareproducedthroughthedrosopterinpathway.Thesepigmentsbindtogranuleswithintheeyestoproducethecharacteristicredeyecolorofwild-typeflies.Homozygousbrownisepistatictoallthegenesinvolvedinthed

6、rosopterinpathwayandhomozygousscarletisepistatictoallthegenesinvolvedintheommochromepathway.ommochromepathwayRedEyesdrosopterinpathwayHomozygousbrownblocksthebindingofredpigmentstoeyegranules,resultinginbrowneyes.ommochromepathwayBrownEyesdrosopterinpathwayHomozy

7、gousscarletblocksthebindingofbrownpigmentstoeyegranules,resultinginbright-redeyesommochromepathwayScarletEyesdrosopterinpathwayIfbothmutationsarepresentinthehomozygouscondition,bothpathwaysareblocked,andthereisnopigmentintheeyes.ommochromepathwayWhiteEyesdrosopte

8、rinpathway©CarolinaBiologicalSupplyCompanyCarolinaBiologicalSupplyCompanygrantsteacherspermissiontophotocopyorreproducebyothermeansthisdocumentinquantitiessuff