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Gregor Mendel: a Study in Scientific Ethics

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Gregor Mendel: a Study in Scientific Ethics GregorGregor Mendel:Mendel: AA StudyStudy inin ScientificScientific EthicsEthics SantoshSantosh ShahShah CapstoneCapstone SummerSummer 20032003 OverviewOverview z GregorGregor MendelMendel z OverviewOverview ofof GeneticsGenetics z MendelMendel’’ss ExperimentalExperimental WorkWork z MendelMendel’’ss DiscoveryDiscovery z RediscoveryRediscovery ofof MendelMendel’’ss WorkWork z QuestioningQuestioning MendelMendel’’ss DataData – SkepticsSkeptics – SupportersSupporters z ConclusionConclusion GregorGregor MendelMendel zz BornBorn 18221822 inin AustriaAustria zz OrdainedOrdained asas priestpriest inin 18471847 zz StudiedStudied NaturalNatural ScienceScience andand PhysicsPhysics 18511851--18531853 zz UndertookUndertook investigationsinvestigations inin hybridizationhybridization ofof plantsplants asas anan abbotabbot inin 18561856 zz DevelopedDeveloped aa modelmodel forfor inheritanceinheritance ofof genesgenes Gregor Mendel (1822-1884) GeneticsGenetics z Gene:Gene: basicbasic unitunit ofof inheritanceinheritance z TwoTwo genes(orgenes(or alleles)alleles) forfor eacheach characteristic:characteristic: oneone fromfrom fatherfather andand oneone fromfrom mothermother z GenesGenes ofof twotwo types:types: DNA Helix dominantdominant oror recessiverecessive z Genotype:Genotype: geneticgenetic makeupmakeup z Phenotype:Phenotype: physicalphysical manifestationmanifestation Monohybrid Cross ExperimentalExperimental WorkWork zz SelectedSelected peapea plantplant forfor itsits numerousnumerous inheritableinheritable characteristics/shapecharacteristics/shape ofof itsits flowerflower zz TracedTraced thesethese characteristics(phenotypes)characteristics(phenotypes) throughthrough severalseveral generationsgenerations zz InferringInferring informationinformation aboutabout genotypesgenotypes Pea Plant CharacteristicsCharacteristics StudiedStudied Shape of ripe seeds Color of Ripe seeds Shape of Pods Height of Mature Plant RegulatingRegulating ConditionsConditions zz UsedUsed brushesbrushes toto pollinatepollinate flowersflowers zz CoveredCovered flowersflowers toto preventprevent naturalnatural fertilizationfertilization zz CoveredCovered podspods fromfrom beingbeing eateneaten zz AllowedAllowed plantsplants toto growgrow inin controlledcontrolled conditionsconditions ExampleExample zz UsedUsed purplepurple andand whitewhite flowersflowers (in(in P)P) zz FoundFound (F1)(F1) hadhad allall purplepurple flowersflowers zz GenerationGeneration (F2)(F2) hadhad purplepurple andand whitewhite flowersflowers inin ratioratio 3:13:1 MendelMendel’’ss DiscoveryDiscovery zz EstablishedEstablished mathematicalmathematical modelmodel forfor inheritanceinheritance patternpattern ofof peapea characteristicscharacteristics zz BroughtBrought experimental/quantitativeexperimental/quantitative approachapproach toto geneticsgenetics zz DevisedDevised thethe lawlaw ofof segregationsegregation zz BroughtBrought ideasideas ofof independentindependent assortment,assortment, coco--dominancedominance toto thethe fieldfield ofof geneticsgenetics zz ExplainedExplained heredityheredity inin purelypurely geneticgenetic termsterms RediscoveryRediscovery ofof MendelMendel z CollectedCollected datadata andand formulatedformulated theorytheory forfor 28,00028,000 peapea plantsplants z PublishedPublished resultsresults withwith theorytheory inin 18531853-- 1854,18661854,1866 z MendelMendel’’ss workwork waswas ignoredignored forfor aa numbernumber ofof yearsyears z HugoHugo dede VriesVries (1848(1848--1935)1935) deviseddevised theorytheory ofof inheritanceinheritance ofof characteristicscharacteristics andand uncovereduncovered MendelMendel whilewhile searchingsearching literatureliterature inin 1900.1900. WhyWhy thethe neglect?neglect? zz PublishedPublished inin 1864,1864, notnot referencedreferenced untiluntil 19001900 zz InaccessibilityInaccessibility ofof paperpaper inin journaljournal VerhandlungenVerhandlungen desdes naturforschendennaturforschenden VereinesVereines inin BrBrüünnnn zz NineteenthNineteenth centurycentury biologistsbiologists consideredconsidered heredityheredity toto bebe relatedrelated toto developmentdevelopment andand didndidn’’tt needneed toto bebe explainedexplained onon itsits ownown zz MendelMendel explainedexplained heredityheredity byby geneticsgenetics butbut nevernever wentwent intointo thethe significancesignificance ofof hishis workwork QuestioningQuestioning ofof DataData z ProfessorProfessor ofof GeneticsGenetics R.A.R.A. FisherFisher (1890(1890--1962)1962) studiedstudied MendelMendel’’ss publicationspublications extensivelyextensively andand reportedreported thatthat MendelMendel hadhad falsifiedfalsified hishis datadata basedbased 2 onon χ analysisanalysis (1936)(1936) z FisherFisher reportedreported thatthat MendelMendel’’ss resultsresults werewere betterbetter thanthan statisticsstatistics eveneven ifif datadata matchedmatched theorytheory exactlyexactly z Example:Example: FlipFlip coincoin 10001000 times:times: –– ObtainingObtaining 500500 headsheads andand 500500 talestales isis mostmost probableprobable butbut stillstill veryvery unlikelyunlikely SupportersSupporters ofof MendelMendel zz FisherFisher’’ss workwork grewgrew muchmuch criticismcriticism becausebecause manymany tooktook itit veryvery seriouslyseriously zz SupportersSupporters feltfelt thatthat accusingaccusing aa luckylucky manman ofof cheatingcheating waswas preposterouspreposterous zz SomeSome feltfelt thatthat FisherFisher’’ss methodsmethods werewere questionablequestionable andand therethere waswas nono proofproof thatthat MendelMendel’’ss datadata waswas fabricatedfabricated ConclusionConclusion zz DidDid MendelMendel falsifyfalsify data?data? –– SomeSome saysay yes,yes, somesome saysay nono –– WeWe maymay nevernever knowknow zz DidDid MendelMendel manipulatemanipulate data?data? –– MostMost likelylikely MendelMendel trimmedtrimmed highlyhighly deviantdeviant valuesvalues suspectingsuspecting thatthat theythey involvedinvolved pollenpollen contaminationcontamination and/orand/or otherother accidentsaccidents –– SinceSince MendelMendel hadhad veryvery littlelittle knowledgeknowledge ofof statistics,statistics, hehe didndidn’’tt knowknow thatthat somesome variationvariation waswas normalnormal andand expectedexpected EthicalEthical IssuesIssues z ItIt isis likelylikely thatthat anan investigatorinvestigator’’ss biasbias maymay inin somesome wayway skewskew thethe datadata z ““GoodGood ScienceScience”” setssets experimentalexperimental conditionsconditions toto counteractcounteract bias.bias. z StatisticalStatistical methodsmethods provideprovide aa wayway toto gaugegauge toto gaugegauge whetherwhether oror notnot ““goodgood sciencescience”” isis beingbeing conductedconducted z MendelMendel mostmost likelylikely didndidn’’tt knowknow thatthat hehe waswas doingdoing anythinganything ““wrongwrong”” byby throwingthrowing outout somesome data.data. ReferencesReferences z www.gsia.cmu.edu/afs/andrew/gsia/biotech/Geneti1.jpg z fates.cns.muskingum.edu/~psych/ psycweb/history/mendel.htm z http://www.mendelweb.org/MWhartl.html z ntri.tamuk.edu/homepage-ntri/lectures/ biology/lecture12.htm z R. A. Fisher. Annals Sci. 1. 115(1936). z The Journal of Heredity 75:501-502 (1984) z The Journal of Heredity 77:218-220 (1986) z The Journal of Heredity 77: 138 (1986) z clab.cecil.cc.md.us/faculty/ biology1/MENDEL.HTM.
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