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. Everyone agreed that McClintock was smart.Rhoades consid-ered her clearly something special, and Beadle used expressionssuch as fantastic, spectacular, and the best job that s beendone. I ve known a lot of famous scientists, Rhoades remarked ina 1980 interview. But the only one I thought really was a genius wasMcClintock. Her brilliance was a given, but some people found her irritat-ing and difficult.She continued to beat people at their own work,as she did with Fitz Randolph and George Beadle, and some peopletook offense, feeling that she was unfair or unwanted competitionand stole their work and their opportunity to gain recognition.InBeadle s case, he and McClintock ended up publishing the resultsjointly in 1928 in a note in Science.He did complain to Emerson,though, who was department chair.According to McClintock,Emerson told him that he should be grateful there was someone 46 BARBARA MCCLINTOCKaround who could explain it.The fun was solving problems, likea game, she added according to science writer Sharon BertschMcGrayne. It was entertaining. Beyond the personal level, McClintock and her cadre of cytoge-neticists differed in approach and orientation from the old-schoolgeneticists who approached the study of inheritance in botanythrough the study of inherited traits by controlled breeding.Theolder group had not had a chance to get used to the approach thatMcClintock and her colleagues were taking.Further, they were notused to the level of accuracy and detail McClintock used to obtainher results.This caused a continuing rift between her and the oldschool. Even she apparently thought of the situation as a battleof the generations, declaring that older people could not join thegroup because they did not have the same intensity about theirwork.Intensity the cytology group definitely had, and McClintockespecially so.She attacked problems in bursts, working on andoff, day and night, until she reached a solution, and she seemedto have boundless energy, taking on physical challenges with thesame unflinching will.Sometimes, the stories told about BarbaraMcClintock are written larger than life, and often facts are notsolid.Stories told in interviews oral history often are told longafter they have occurred and memories have become faded andcompressed.Women and girls looking for role models and heroeshave embellished true stories.McClintock s own love of a good storyhas doubtless sometimes augmented a tale.McClintock, a basicallyprivate person, occasionally seems to have created facades to hidebehind.One such tale writ large is the story of the parched corn-field, as reported by biographer Nathaniel C.Comfort.No proof hasturned up to authenticate the tale.No document has ever justified itsplace in the factual history of this remarkable woman s life.Perhapssomething like it did happen.As the tale begins one wants to say, Once upon a time. When she was in danger of losing an entirecrop to a prolonged dry spell, she laid an irrigation line of water pipeup to the hilltop where her cornfield was withering in the hot sun,ignoring her own pain from the blistering work as tears rolled downher cheeks.When a nighttime flood washed out her newly planted Scientist at Work 47kernels, she replanted the entire patch working virtually in the darkexcept for the dim light offered by a pair of car headlights.McClintock and Creighton Team UpIn the summer of 1929, a young graduate student in botany arrivedon the Cornell campus.Her name was Harriet Creighton.She was21 years old and a graduate of Wellesley College, a student of Dr.Margaret Ferguson, who had taught science at Wellesley for 26years.No doubt recognizing intelligence and a talent for science inCreighton, Ferguson had encouraged her to attend graduate schoolat Cornell.When Creighton arrived, she was assigned as a graduate teachingassistant to paleobotanist Loren C.Petry in the botany departmentin the College of Agriculture at Cornell.She was planning to studyeither plant physiology or cytology.On Creighton s first day, howev-er, she met Barbara McClintock, who immediately began to changeCreighton s plans.She set up Sharp as Creighton s adviser andarranged the younger woman s course of study, settling on a major ingenetics and cytology and a minor in plant physiology.McClintockadvised going straight for a doctorate, skipping the master s degreean unusual plan at the time, one intended to send a message of com-mitment and confidence.McClintock took charge perhaps becauseCreighton was a woman and McClintock knew there would beobstacles to overcome, perhaps because she saw something of herselfin this young student, or perhaps because McClintock was lookingahead to the day when she would leave and Sharp would need a newassistant for his cytogenetics class.Looking back, Creighton thoughtthe last possibility was the most likely.In any case, McClintockhanded Creighton a lot of advice, and Creighton listened well.It wasthe beginning of a lifelong friendship.Like Charles Burnham, who arrived at Cornell at about thesame time, Harriet Creighton was also welcomed into the cytologygroup formed by McClintock, Rhoades, and Beadle.Creighton soonbecame an able research partner to McClintock, and McClintock,just two years after completing her own Ph.D., magnanimously oper-ated by a dictum she learned from Rollins Emerson.When handing 48 BARBARA MCCLINTOCKout a research project to a fresh, new student, he advised, offer thevery best and most promising problem you have. And that is exactlywhat McClintock did.The problem offered to Creighton was the challenge to showdefinitive, physical proof that during meiosis in maize, some of oneparent s genes, along with the segment of chromosome on whichthey were located, physically crossed over to the other parent shomologous (similar) chromosome.Breeders and genetics research-ers like Mendel had observed for a long time that offspring showedthe effects of combined traits from both parents.Moreover, Morganhad hypothesized that very process.Now, McClintock believed, theycould show physical proof of crossover by using hands-on cytologi-cal techniques.Once Creighton was finished, scientists would knowmuch more about how crossovers worked.The ExperimentThe project had two parts.For the first part, they needed to find aset of markers stainable, unique features located on a chromo-some that usually carried a set of linked genes.This setup wouldenable the two scientists to track the chromosome through theprocess of crossing-over.For the second part, they needed to findan easily observed set of genetic markers expressed in the pheno-type on the same chromosome, so they could verify the simultane-ous crossover movement of both the genes and the chromosomes.McClintock had already done some of the work.She had founda suitable group of linked genes and had established that they allwere located on the same chromosome [ Pobierz całość w formacie PDF ] |
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