A Short History of Nearly Everything- 第88部分

clearly　there　was　a　need　for　some　inspired　and　clever　experimentation；　and　happily　the　ageproduced　a　young　person　with　the　diligence　and　aptitude　to　undertake　it。　his　name　wasthomas　hunt　morgan；　and　in　1904；　just　four　years　after　the　timely　rediscovery　of　mendel’sexperiments　with　pea　plants　and　still　almost　a　decade　before　gene　would　even　bee　a　word；he　began　to　do　remarkably　dedicated　things　with　chromosomes。

chromosomes　had　been　discovered　by　chance　in　1888　and　were　so　called　because　theyreadily　absorbed　dye　and　thus　were　easy　to　see　under　the　microscope。　by　the　turn　of　thetwentieth　century　it　was　strongly　suspected　that　they　were　involved　in　the　passing　on　of　traits；but　no　one　knew　how；　or　even　really　whether；　they　did　this。

morgan　chose　as　his　subject　of　study　a　tiny；　delicate　fly　formally　called　drosophilamelanogaster；　but　more　monly　known　as　the　fruit　fly　（or　vinegar　fly；　banana　fly；　orgarbage　fly）。　drosophila　is　familiar　to　most　of　us　as　that　frail；　colorless　insect　that　seems　tohave　a　pulsive　urge　to　drown　in　our　drinks。　as　laboratory　specimens　fruit　flies　had　certainvery　attractive　advantages：　they　cost　almost　nothing　to　house　and　feed；　could　be　bred　by　themillions　in　milk　bottles；　went　from　egg　to　productive　parenthood　in　ten　days　or　less；　and　hadjust　four　chromosomes；　which　kept　things　conveniently　simple。

working　out　of　a　small　lab　（which　became　known　inevitably　as　the　fly　room）　inschermerhorn　hall　at　columbia　university　in　new　york；　morgan　and　his　team　embarked　ona　program　of　meticulous　breeding　and　crossbreeding　involving　millions　of　flies　（onebiographer　says　billions；　though　that　is　probably　an　exaggeration）；　each　of　which　had　to　becaptured　with　tweezers　and　examined　under　a　jeweler’s　glass　for　any　tiny　variations　ininheritance。　for　six　years　they　tried　to　produce　mutations　by　any　means　they　could　think　of—zapping　the　flies　with　radiation　and　x…rays；　rearing　them　in　bright　light　and　darkness；　bakingthem　gently　in　ovens；　spinning　them　crazily　in　centrifuges—but　nothing　worked。　morgan　wason　the　brink　of　giving　up　when　there　occurred　a　sudden　and　repeatable　mutation—a　fly　thathad　white　eyes　rather　than　the　usual　red　ones。　with　this　breakthrough；　morgan　and　hisassistants　were　able　to　generate　useful　deformities；　allowing　them　to　track　a　trait　throughsuccessive　generations。　by　such　means　they　could　work　out　the　correlations　betweenparticular　characteristics　and　individual　chromosomes；　eventually　proving　to　more　or　lesseveryone’s　satisfaction　that　chromosomes　were　at　the　heart　of　inheritance。

the　problem；　however；　remained　the　next　level　of　biological　intricacy：　the　enigmatic　genesand　the　dna　that　posed　them。　these　were　much　trickier　to　isolate　and　understand。　aslate　as　1933；　when　morgan　was　awarded　a　nobel　prize　for　his　work；　many　researchers　stillweren’t　convinced　that　genes　even　existed。　as　morgan　noted　at　the　time；　there　was　noconsensus　“as　to　what　the　genes　are—whether　they　are　real　or　purely　fictitious。”　it　may　seemsurprising　that　scientists　could　struggle　to　accept　the　physical　reality　of　something　sofundamental　to　cellular　activity；　but　as　wallace；　king；　and　sanders　point　out　in　biology：　thescience　of　life　（that　rarest　thing：　a　readable　college　text）；　we　are　in　much　the　same　positiontoday　with　mental　processes　such　as　thought　and　memory。　we　know　that　we　have　them；　ofcourse；　but　we　don’t　know　what；　if　any；　physical　form　they　take。　so　it　was　for　the　longest　timewith　genes。　the　idea　that　you　could　pluck　one　from　your　body　and　take　it　away　for　study　wasas　absurd　to　many　of　morgan’s　peers　as　the　idea　that　scientists　today　might　capture　a　straythought　and　examine　it　under　a　microscope。

what　was　certainly　true　was　that　something　associated　with　chromosomes　was　directingcell　replication。　finally；　in　1944；　after　fifteen　years　of　effort；　a　team　at　the　rockefellerinstitute　in　manhattan；　led　by　a　brilliant　but　diffident　canadian　named　oswald　avery；succeeded　with　an　exceedingly　tricky　experiment　in　which　an　innocuous　strain　of　bacteria　wasmade　permanently　infectious　by　crossing　it　with　alien　dna；　proving　that　dna　was　far　morethan　a　passive　molecule　and　almost　certainly　was　the　active　agent　in　heredity。　the　austrian…born　biochemist　erwin　chargaff　later　suggested　quite　seriously　that　avery’s　discovery　wasworth　two　nobel　prizes。

unfortunately；　avery　was　opposed　by　one　of　his　own　colleagues　at　the　institute；　a　strong…willed　and　disagreeable　protein　enthusiast　named　alfred　mirsky；　who　did　everything　in　hispower　to　discredit　avery’s　work—including；　it　has　been　said；　lobbying　the　authorities　at　thekarolinska　institute　in　stockholm　not　to　give　avery　a　nobel　prize。　avery　by　this　time　wassixty…six　years　old　and　tired。　unable　to　deal　with　the　stress　and　controversy；　he　resigned　hisposition　and　never　went　near　a　lab　again。　but　other　experiments　elsewhere　overwhelminglysupported　his　conclusions；　and　soon　the　race　was　on　to　find　the　structure　of　dna。

had　you　been　a　betting　person　in　the　early　1950s；　your　money　would　almost　certainly　havebeen　on　linus　pauling　of　caltech；　america’s　leading　chemist；　to　crack　the　structure　of　dna。

pauling　was　unrivaled　in　determining　the　architecture　of　molecules　and　had　been　a　pioneer　inthe　field　of　x…ray　crystallography；　a　technique　that　would　prove　crucial　to　peering　into　theheart　of　dna。　in　an　exceedingly　distinguished　career；　he　would　win　two　nobel　prizes　（forchemistry　in　1954　and　peace　in　1962）；　but　with　dna　he　became　convinced　that　the　structurewas　a　triple　helix；　not　a　double　one；　and　never　quite　got　on　the　right　track。　instead；　victory　fellto　an　unlikely　quartet　of　scientists　in　england　who　didn’t　work　as　a　team；　often　weren’t　onspeaking　terms；　and　were　for　the　most　part　novices　in　the　field。

of　the　four；　the　nearest　to　a　conventional　boffin　was　maurice　wilkins；　who　had　spent　muchof　the　second　world　war　helping　to　design　the　atomic　bomb。　two　of　the　others；　rosalindfranklin　and　francis　crick；　had　passed　their　war　years　working　on　mines　for　the　britishgovernment—crick　of　the　type　that　blow　up；　franklin　of　the　type　that　produce　coal。

the　most　unconventional　of　the　foursome　was　james　watson；　an　american　prodigy　whohad　distinguished　himself　as　a　boy　as　a　member　of　a　highly　popular　radio　program　called　thequiz　kids　（and　thus　could　claim　to　be　at　least　part　of　the　inspiration　for　some　of　the　membersof　the　glass　family　in　franny　and　zooey　and　other　works　by　j。　d。　salinger）　and　who　hadentered　the　university　of　chicago　aged　just　fifteen。　he　had　earned　his　ph。d。　by　the　age　oftwenty…two　and　was　now　attached　to　the　famous　cavendish　laboratory　in　cambridge。　in1951；　he　was　a　gawky　twenty…three…year…old　with　a　strikingly　lively　head　of　hair　that　appearsin　photographs　to　be　straining　to　attach　itself　to　some　powerful　magnet　just　out　of　frame。

crick；　twelve　years　older　and　still　without　a　doctorate；　was　less　memorably　hirsute　andslightly　more　tweedy。　in　watson’s　account　he　is　presented　as　blustery；　nosy；　cheerfullyargumentative；　impatient　with　anyone　slow　to　share　a　notion；　and　constantly　in　danger　ofbeing　asked　to　go　elsewhere。　neither　was　formally　trained　in　biochemistry。

their　assumption　was　that　if　you　could　determine　the　shape　of　a　dna　molecule　you　wouldbe　able　to　see—correctly；　as　it　turned　out—how　it　did　what　it　did。　they　hoped　to　achieve　this；it　would　appear；　by　doing　as　little　work　as　possible　beyond　thinking；　and　no　more　of　that　thanwas　absolutely　necessary。　as　watson　cheerfully　（if　a　touch　disingenuously）　remarked　in　hisautobiographical　book　the　double　helix；　“it　was　my　hope　that　the　gene　might　be　solvedwithout　my　learning　any　chemistry。”　they　weren’t　actually　assigned　to　work　on　dna；　and　atone　point　were　ordered　to　stop　it。　watson　was　ostensibly　mastering　the　art　of　crystallography；crick　was　supposed　to　be　pleting　a　thesis　on　the　x…ray　diffraction　of　large　molecules。

although　crick　and　watson　enjoy　nearly　all　the　credit　in　popular　accounts　for　solving　themystery　of　dna；　their　breakthrough　was　crucially　dependent　on　experimental　work　done　bytheir　petitors；　the　results　of　which　were　obtained　“fortuitously；”　in　the　tactful　words　of　thehistorian　lisa　jardine。　far　ahead　of　them；　at　least　at　the　beginning；　were　two　academics　atking’s　college　in　london；　wilkins　and　franklin。

the　new　zealand–born　wilkins　was　a　retiring　figure；　almost　to　the　point　of　invisibility。　a1998　pbs　documentary　on　the　discovery　of　the　structure　of　dna—a　feat　for　which　he　sharedthe　1962　nobel　prize　with　crick　and　watson—managed　to　overlook　him　entirely。

the　most　enigmatic　character　of　all　was　franklin。　in　a　severely　unflattering　portrait；watson　in　the　double　helix　depicted　franklin　as　a　woman　who　was　unreasonable；　secretive；chronically　uncooperative；　and—this　seemed　especially　to　irritate　him—almost　willfullyunsexy。　he　allowed　that　she　“was　not　unattractive　and　might　have　been　quite　stunning　had　shetaken　even　a　mild　interest　in　clothes；”　but　in　this　she　disappointed　all　expectations。　she　didn’teven　use　lipstick；　he　noted　in　wonder；　while　her　dress　sense　“showed　all　the　imagination　ofenglish　blue…stocking　adolescents。”

1however；　she　did　have　the　best　images　in　existence　of　the　possible　structure　of　dna；achieved　by　means　of　x…ray　crystallography；　the　technique　perfe