NATIONAL ACADEMY OF SCIENCES A LFRED HENRY S TURTEVANT 1891—1970 A Biographical Memoir by E D WA R D B . L E W IS Any opinions expressed in this memoir are those of the author(s) and do not necessarily reflect the views of the National Academy of Sciences. Biographical Memoir COPYRIGHT 1998 NATIONAL ACADEMIES PRESS WASHINGTON D.C. CourtesyoftheInstituteArchives,CaliforniaInstitueofTechnology,Pasadena ALFREDHENRYSTURTEVANT November21,1891—April5,1970 BYEDWARDB.LEWIS TURTEVANTWASTHEyoungestofsixchildrenofAlfred SHenrySturtevantandHarrietEvelynMorse.Hisgrand- fatherJulianM.SturtevantgraduatedfromYaleDivinity SchoolandwasafounderandlaterpresidentofIllinois College.Sturtevant’sfathertaughtmathematicsforatime atIllinoisCollegebutsubsequentlyturnedtofarming,first inIllinoisandlaterinsouthernAlabama,wherethefamily movedwhenSturtevantwasseven.Hisearlyeducationwas inAlabamainaone-roomcountryschool,butforthelast threeyearsofhighschoolhewenttoapublicschoolin Mobile. Inthefallof1908SturtevantenteredColumbiaUniver- sity.Thechoice,acrucialone,wasmadebecauseSturtevant’s oldestbrother,Edgar,wasthenteachingLatinandGreek atBarnardCollege;Edgarandhiswifemadeitpossible forSturtevanttoattendtheuniversitybytakinghiminto theirhome.SturtevantwasgreatlyinfluencedbyEdgar, fromwhomhelearnedtheaimsandstandardsofscholar- shipandresearch. AsaboySturtevanthaddrawnupthepedigreesofhis father’shorsesandofhisownfamily.Hepursuedthisinter- ReprintedwithpermissionfromDictionaryofScientificBiography,vol.13,pp.133-38. NewYork:Chas.Scribner’sSons,1976. 3 4 BIOGRAPHICALMEMOIRS estasahobbywhilehewasatColumbia.Edgarencouraged himtoreadworksonheredityandtolearnmore aboutthemeaningofpedigrees.AsaresultSturtevant readabookonMendelismbyPunnettthatgreatlystimu- latedhisinterest,sincehesawhowMendel’sprinciples couldbeusedtoexplainthepatternofinheritanceof certaincoatcolorsinhorses.EdgarsuggestedthatSturtevant workoutthegeneticrelationships,writeanaccountofhis findings,andsubmitittoThomasHuntMorgan,whoheld thechairofexperimentalzoologyatColumbiaandfrom whomSturtevanthadalreadytakenacourse.Morganclearly wasimpressed,sincehenotonlyencouragedSturtevantto publishtheaccount,whichappearedinBiologicalBulletin in1910,butalso,inthefallofthatyear,gaveSturtevanta deskinhislaboratory,whichcametobeknownasthe“fly room.”Onlyafewmonthsbefore,Morganhadfoundthe firstwhite-eyedmutantinDrosophilaandhadworkedout theprinciplesofsexlinkage. AftercompletinghisdoctoralworkwithMorganin1914, SturtevantremainedatColumbiaasaresearchinvestiga- torfortheCarnegieInstitutionofWashington.Hewasa memberofaresearchteamthatMorganhadassembleda fewyearsearlierandthatconsistedprincipallyoftwoother studentsofMorgan’s,C.B.BridgesandH.J.Muller.The “flyroom”inwhichtheyconductedalloftheirexperi- mentswasonlysixteenbytwenty-threefeet,andattimes asmanyaseightpeoplehaddesksinit.Accordingto Sturtevant,theatmospherewasoneofhighexcitement, eachnewideabeingfreelyputforthanddebated.Morgan, Bridges,andSturtevantremainedatColumbiauntil1928; Mullerleftthegroupin1921totakeapositionatthe UniversityofTexas. In1922SturtevantmarriedPhoebeCurtisReed;andin thesameyeartheymadetheirfirsttriptoEurope,visiting ALFREDHENRYSTURTEVANT 5 museumsandlaboratoriesinEngland,Norway,Sweden, andHolland.Theyhadthreechildren. In1928SturtevantmovedtoPasadenatobecomepro- fessorofgeneticsinthenewdivisionofbiologythatMor- ganhadestablishedinthatyearattheCaliforniaInstitute ofTechnology.Muchofthesamestimulatingatmosphere andunpretentiouswayofconductingsciencethatMorgan andhisstudentshadpracticedatColumbiawastransferred tothenewKerckhoffLaboratoryatCaltech.Sturtevant becametheacknowledgedandnaturalleaderofthenew geneticsgroupestablishedthere.Hemaintainedanactive researchprograminwhichheoftencollaboratedwithother membersofthegeneticsstaff,includingGeorgeW.Beadle, TheodosiusDobzhansky,SterlingEmerson,andJackSchultz. Hegavelecturesinthegeneralbiologycourseandtaught elementaryandadvancedcoursesingeneticsand,onocca- sion,acourseinentomology.HeremainedatCaltechuntil hisdeathexceptforayearinEnglandandGermanyin 1932,asvisitingprofessoroftheCarnegieEndowmentfor InternationalPeace,andshorterperiodswhenheheldvis- itingprofessorshipsatanumberofAmericanuniversities. Hereceivedmanyhonors,includingtheNationalMedal ofSciencein1968. Inadditiontohisprincipalpublicationsdealingwith thegeneticsandtaxonomyofDrosophila,Sturtevantcon- tributedpapersonthegeneticsofhorses,fowl,mice,moths, snails,iris,andespeciallytheeveningprimroses(Oenothera). Althoughhischiefcontributionsareingenetics,hewas alsoaleadingauthorityonthetaxonomyofseveralgroups ofDiptera,especiallythegenusDrosophila,ofwhichhe describedmanynewspecies.Hewasmuchinterestedin thesocialinsectsandpublishedseveralpapersonthebe- haviorofants. 6 BIOGRAPHICALMEMOIRS Sturtevanthadaprodigiousmemoryandtrulyencyclo- pedicinterests.Hehadanaturalbentformathematicsbut littleformaltraininginit.Heespeciallyenjoyed,andwas expertatsolving,allkindsofpuzzles,especiallythosein- volvinggeometricalsituations.Forhimscientificresearch wasanexcitingandrewardingactivitynotunlikepuzzle- solving.acommonthemeofhisinvestigationswasanef- forttoanalyzeandexplainexceptionstoestablishedprin- ciples. Sturtevantknewhowtodesignandexecutesimple,el- egantexperiments,describingtheresultsinconcise,lucid prose.Hesethighstandardsforhisownresearchand expectedotherstodothesame. Sturtevant’sdiscoveriesoftheprincipleofgenemap- ping,ofthefirstreparablegenedefect,oftheprinciple underlyingfatemapping,ofthephenomenaofunequal crossing-over,andofpositioneffectwereperhapshisgreatest scientificachievements.Theaccountoftheseandsomeof hisothermajorcontributionstoscienceisarrangedin approximatechronologicalorder. Mendelhadfoundthatallofthehereditaryfactorswith whichheworkedassortedindependentlyofoneanotherat thetimeofgameteformation.Exceptionstothissecond Mendelianlawbegantoaccumulatein1900-1909.Morgan wasthefirsttoprovideasatisfactoryexplanationforsuch exceptionsintermsofahypothesis,whichassumesthat genestendingtoremaintogetherinpassingfromonegen- erationtothenextmustbelocatedinthesamechromo- some.Hefurtherpostulatedthattheextenttowhichsuch linkedgenesrecombineatmeiosisisarelativemeasureof theirphysicaldistance. Sturtevantintroducedtheconceptthatthefrequencyof crossing-overbetweentwogenesfurnishesanindexoftheir distanceonalineargeneticmap.Heproposedthat1per- ALFREDHENRYSTURTEVANT 7 centofcrossing-overbetakenasequaltoonemapunit.He thenreasonedthatifthedistancebetweentwogenes,A andB,isequaltoxmapunitsandthedistancebetweenB andathirdgene,C,isequaltoymapunits,thenthedis- tancebetweenAandCwillbex+yifBisthemiddlegene; x–yifCisthemiddlegene,andy–xifAisthemiddle gene.ThegermofthisideaoccurredtoSturtevantincon- versationwithMorgan.InhisHistoryofGenetics,Sturtevant recordedthathe“wenthome,andspentmostofthenight (totheneglectofmyundergraduatehomework)inpro- ducingthefirstchromosomemap,includingthelinkedgenes, y,w,v,m,andr,inthatorder,andapproximatelytherela- tivespacing,astheystillappearonthestandardmaps”(p. 47). Sturtevantdevisedacrucialtestoftheprinciplesofmap- pinggenesbyconstructingcrossesinwhichallthreegenes weresegregatingsimultaneously.Intheprogenyofsuch “three-factor”crosses,Sturtevantdiscoveredthatdouble crossing-overcanoccurandthatitsfrequencyisequalto, orlessthan,theproductofthetwosinglecrossing-over frequencies.Conversely,thefrequencyofdoublecrossing- overcanbeusedtodeducetheorderofthethreegenes. Sturtevantshowedthattheorderobtainedfromtwo-factor crosseswasfullyconfirmedandthatthethree-factorcrosses providedamorepowerfulmethodoforderingandmap- pinggenesthandidtwo-factorcrosses.Hepublishedthese findingsin1913.Hisprinciplesandmethodsofchromo- somemappinghaveenabledgeneticiststomapthechro- mosomesofawidevarietyofhigherorganisms,including man. Sturtevantwasasmuchconcernedwiththeroleofgenes indevelopmentaswiththelawsgoverningtheirtransmis- sionfromonegenerationtothenext.In1915hepub- lishedanaccountofthesexualbehaviorofDrosophilathat 8 BIOGRAPHICALMEMOIRS includedastudyofsexualselectionbasedontheuseof specificmutantgenesthatalteredtheeyecolororbody colorofthefly.Thisworkwastheforerunnerofanexten- sivelineofresearchbyothersandconstitutedoneofthe firstexamplesoftheuseofspecificmutantgenestodis- sectthebehaviorofanorganism. Oneofthemoreconspicuousrolesthatgenesplayin developmentistheircontroloftheprocessesofsexual differentiation.In1919Sturtevantreportedthefirstcase inwhichintersexualitycouldbeshowntoresultfromthe presenceofspecificrecessivegenes.Yearslaterhefounda similartypeofgenethatresultedinthevirtuallycomplete transformationoffemalesintomales.Mutantsofstillother “sexgenes”havebeenfoundinDrosophilaandinmany otherorganisms,includingman.Asaresult,sexhascome tobeviewedasacomplextraitcontrolledbyanumberof differentgenes,mutantsofwhichcanbeexpectedtopro- ducevariousgradesofintersexuality. Sturtevantpioneeredinprovidingexperimentalap- proachestoacentralprobleminbiology—howgenespro- ducetheireffects.Animportantbreak-throughcamein 1920,withhisdiscoveryofthefirstreparablegenedefect. InstudyinggynandromorphsofDrosophilainwhichthere wassomaticmosaicismforthevermilioneye-colormutant, henoticedthattheeyesdevelopedthedarkredcolorof thewildtypeinsteadofthebrightredcolorofthevermil- ionmutant,evenwhentheeyecouldbeshowntobege- neticallyvermilion.Evidently,vermilioneyetissuelacked somesubstancethatcouldbesuppliedbygenetically nonvermiliontissuefromanotherportionofthebody.As G.W.Beadlepointedout,muchofmodernbiochemical geneticsstemsdirectlyfromthisearlywork. Sturtevanthadshownin1913thatforeachofthemajor chromosomesofDrosophilathereisacorrespondinglink- ALFREDHENRYSTURTEVANT 9 agemap.Heandothershadnoticed,however,thatexces-