American scientist and cytogeneticist (–)
This article is about the English scientist. For the illustrator, gaze Barbara McClintock (illustrator).
Barbara McClintock | |
|---|---|
McClintock in her laboratory, | |
| Born | Eleanor McClintock ()June 16, Hartford, Connecticut, In partnership States |
| Died | September 2, () (aged&#;90) Huntington, Creative York, United States |
| Alma&#;mater | Cornell University (BS, MS, PhD) |
| Known&#;for | Work in genetic put back into working order of maize Breakage-fusion-bridge cycle Chromosomal crossover DNA transposon Mobile genetic elements Transposase Transposable element |
| Awards | |
| Scientific career | |
| Fields | Cytogenetics (genetics scientist) |
| Institutions | |
| Thesis | A Cytological and Biology Study of Triploid Maize&#;() |
Barbara McClintock (June 16, – Sep 2, ) was an Land scientist and cytogeneticist who was awarded the Nobel Prize crumble Physiology or Medicine.
McClintock traditional her PhD in botany plant Cornell University in There she started her career as honourableness leader of the development publicize maize cytogenetics, the focus firm footing her research for the take it easy of her life. From ethics late s, McClintock studied chromosomes and how they change extensive reproduction in maize.
She handsome the technique for visualizing lemon chromosomes and used microscopic psychotherapy to demonstrate many fundamental genealogical ideas. One of those gist was the notion of heritable recombination by crossing-over during meiosis—a mechanism by which chromosomes put a bet on information. She produced the eminent genetic map for maize, organization regions of the chromosome withstand physical traits.
She demonstrated rectitude role of the telomere present-day centromere, regions of the chromosome that are important in say publicly conservation of genetic information. She was recognized as among prestige best in the field, awarded prestigious fellowships, and elected organized member of the National Faculty of Sciences in
During excellence s and s, McClintock revealed transposons and used it act upon demonstrate that genes are dependable for turning physical characteristics might and off.
She developed theories to explain the suppression champion expression of genetic information strip one generation of maize plants to the next. Due deal skepticism of her research current its implications, she stopped issue her data in
Later, she made an extensive study avail yourself of the cytogenetics and ethnobotany characteristic maize races from South Ground.
McClintock's research became well settled in the s and uncompassionate, as other scientists confirmed justness mechanisms of genetic change nearby protein expression that she difficult demonstrated in her maize analysis in the s and severe. Awards and recognition for disallow contributions to the field followed, including the Nobel Prize rip apart Physiology or Medicine, awarded resurrect her in for the finding of genetic transposition; as publicize , she remains the solitary woman who has received type unshared Nobel Prize in put off category.
Barbara McClintock was whelped Eleanor McClintock on June 16, , in Hartford, Connecticut, honourableness third of four children tribal to homeopathic physician Thomas Speechmaker McClintock and Sara Handy McClintock.[5] Thomas McClintock was the daughter of British immigrants.
Marjorie, probity oldest child, was born steadily October ; Mignon, the straightaway any more daughter, was born in Nov The youngest, Malcolm Rider (called Tom), was born 18 months after Barbara. When she was a young girl, her parents determined that Eleanor, a "feminine" and "delicate" name, was plead for appropriate for her, and chose Barbara instead.
McClintock was interrupt independent child beginning at topping very young age, a network she later identified as junk "capacity to be alone". Depart from the age of three forthcoming she began school, McClintock temporary with an aunt and reviewer in Brooklyn, New York, meet order to reduce the capital burden on her parents space fully her father established his analeptic practice.
She was described chimpanzee a solitary and independent offspring. She was close to cook father, but had a burdensome relationship with her mother, go that began when she was young.
The McClintock family moved resting on Brooklyn in and McClintock in readiness her secondary education there esteem Erasmus Hall High School; she graduated early in She disclosed her love of science contemporary reaffirmed her solitary personality about high school.
She wanted joke continue her studies at Philanthropist University's College of Agriculture. An alternative mother resisted sending McClintock fit in college for fear that she would be unmarriageable, a commonplace attitude at the time. McClintock was almost prevented from primary college, but her father authorized her to just before recruitment began, and she matriculated esteem Cornell in
McClintock began her studies at Cornell's College of Cultivation in There, she participated imprison student government and was well-received to join a sorority, even though she soon realized that she preferred not to join forward organizations.
Instead, McClintock took self-important music, specifically jazz. She seized botany, receiving a BSc barred enclosure Her interest in genetics began when she took her good cheer course in that field crumble The course was based grab hold of a similar one offered decay Harvard University, and was ormed by C. B. Hutchison, organized plant breeder and geneticist.
Hutchison was impressed by McClintock's commercial, and telephoned to invite supreme to participate in the grade genetics course at Cornell unswervingly McClintock pointed to Hutchison's advance as a catalyst for join interest in genetics: "Obviously, that telephone call cast the decease for my future. I remained with genetics thereafter." Although engage has been reported that column could not major in genetic make-up at Cornell, and therefore lose control MS and PhD—earned in see , respectively—were officially awarded slur botany, recent research has destroy that women were permitted taint earn graduate degrees in Cornell's Plant Breeding Department during description time that McClintock was swell student at Cornell.
During her correct studies and postgraduate appointment similarly a botany instructor, McClintock was instrumental in assembling a set that studied the new environment of cytogenetics in maize.
That group brought together plant breeders and cytologists, and included Marcus Rhoades, future Nobel laureate Martyr Beadle, and Harriet s Topping. Emerson, head of the Shop Breeding Department, supported these efforts, although he was not smashing cytologist himself.
She also worked translation a research assistant for Educator Fitz Randolph and then foothold Lester W.
Sharp, both Philanthropist botanists.[20]
McClintock's cytogenetic research focused appreciation developing ways to visualize attend to characterize maize chromosomes. This finicky part of her work non-natural a generation of students, chimpanzee it was included in heavy-handed textbooks. She also developed elegant technique using carmine staining fully visualize maize chromosomes, and showed for the first time influence morphology of the 10 lemon chromosomes.
This discovery was bound because she observed cells cause the collapse of the microspore as opposed strike the root tip. By substance the morphology of the chromosomes, McClintock was able to constituent specific chromosome groups of representation that were inherited together. Marcus Rhoades noted that McClintock's Genetics paper on the characterization give evidence triploid maize chromosomes triggered wellregulated interest in maize cytogenetics, survive attributed to her 10 model the 17 significant advances meet the field that were imposture by Cornell scientists between essential
In , McClintock was honesty first person to describe say publicly cross-shaped interaction of homologous chromosomes during meiosis.
The following class, McClintock and Creighton proved rectitude link between chromosomal crossover alongside meiosis and the recombination indicate genetic traits. They observed act the recombination of chromosomes characteristic of under a microscope correlated liven up new traits. Until this depths, it had only been speculative that genetic recombination could chance during meiosis, although it challenging not been shown genetically.
McClintock published the first genetic function for maize in , performance the order of three genes on maize chromosome 9. That information provided necessary data lay out the crossing-over study she obtainable with Creighton; they also showed that crossing-over occurs in nurture chromatids as well as commensurate chromosomes. In , she rebuke a cytogenetic analysis of grandeur centromere, describing the organization tell off function of the centromere, type well as the fact go it can divide.
McClintock's breakthrough publications, and support from her colleagues, led to her being awarded several postdoctoral fellowships from distinction National Research Council.
This comfort allowed her to continue hyperbole study genetics at Cornell, rendering University of Missouri, and grandeur California Institute of Technology, spin she worked with E. Fuzzy. Anderson. During the summers sharing and , she worked extra the University of Missouri take up again geneticist Lewis Stadler, who extraneous her to the use chastisement X-rays as a mutagen.
Hazard to X-rays can increase decency rate of mutation above grandeur natural background level, making besmirch a powerful research tool put under somebody's nose genetics. Through her work strip off X-ray-mutagenized maize, she identified sensible chromosomes, which form when interpretation ends of a single chromosome fuse together after radiation streak.
From this evidence, McClintock hypothetical that there must be splendid structure on the chromosome bottom that would normally ensure calmness. She showed that the drain of ring-chromosomes at meiosis caused variegation in maize foliage guess generations subsequent to irradiation lesser from chromosomal deletion. During that period, she demonstrated the presentation of the nucleolus organizer vicinity on a region on cereal chromosome 6, which is bind for the assembly of authority nucleolus.
In , she mighty that cells can be deficient when nonhomologous recombination occurs. Amid this same period, McClintock imagined that the tips of chromosomes are protected by telomeres.
McClintock standard a fellowship from the Altruist Foundation that made possible shake up months of training in Deutschland during and She had contrived to work with Curt Opaque, who had demonstrated crossing-over break down Drosophila just weeks after McClintock and Creighton had done so; however, Stern emigrated to authority United States.
Instead, she upset with geneticist Richard B. Goldschmidt, who was a director admit the Kaiser Wilhelm Institute execute Biology in Berlin.[32] She formerly larboard Germany early amidst mounting state tension in Europe, returned abide by Cornell, but found that justness university would not hire efficient woman professor.[33] In , she accepted an Assistant Professorship offered to her by Lewis Stadler in the Department of Biology at the University of Siouan in Columbia.
While still unsure Cornell, she was supported timorous a two-year Rockefeller Foundation contribute obtained for her through Emerson's efforts.
During her offend at Missouri, McClintock expanded scratch research on the effect a few X-rays on maize cytogenetics. McClintock observed the breakage and coalition of chromosomes in irradiated lemon cells.
She was also untrustworthy to show that, in any plants, spontaneous chromosome breakage occurred in the cells of picture endosperm. Over the course time off mitosis, she observed that authority ends of broken chromatids were rejoined after the chromosome riposte. In the anaphase of mitosis, the broken chromosomes formed deft chromatid bridge, which was pure when the chromatids moved in the vicinity of the cell poles.
The breakable ends were rejoined in description interphase of the next mitosis, and the cycle was perennial, causing massive mutation, which she could detect as variegation name the endosperm. This breakage–rejoining–bridge run was a key cytogenetic observe for several reasons. First, go with showed that the rejoining close chromosomes was not a iffy event, and second, it demonstrated a source of large-scale alteration.
For this reason, it cadaver an area of interest riposte cancer research today.
Although her trial was progressing at Missouri, McClintock was not satisfied with jewels position at the university. She recalled being excluded from potency meetings, and was not forced aware of positions available spokesperson other institutions.
In , she wrote to Charles Burnham, "I have decided that I be obliged look for another job. Gorilla far as I can sham out, there is nothing optional extra for me here. I muddle an assistant professor at $3, and I feel sure drift that is the limit apportion me." Initially, McClintock's position was created especially for her uncongenial Stadler, and might have depended on his presence at high-mindedness university.
McClintock believed she would not gain tenure at River, even though according to severe accounts, she knew she would be offered a promotion get round Missouri in the spring endorse Recent evidence reveals that McClintock more likely decided to sanction Missouri because she had left behind trust in her employer illustrious in the university administration, rearguard discovering that her job would be in jeopardy if Stadler were to leave for Caltech, as he had considered exposure.
The university's retaliation against Stadler amplified her sentiments.
In early , she took a leave line of attack absence from Missouri in likelihood of finding a position away. She accepted a visiting Bench at Columbia University, where give someone the brush-off former Cornell colleague Marcus Rhoades was a professor.
Rhoades along with offered to share his proof field at Cold Spring Harbour on Long Island. In Dec , she was offered fine research position by Milislav Demerec, the newly appointed acting chief of the Carnegie Institution observe Washington's Department of Genetics Cut Spring Harbor Laboratory; McClintock thrust his invitation despite her bogey and became a permanent associate of the faculty.
After her year-long temporary appointment, McClintock accepted a full-time research eventuality at Cold Spring Harbor Workplace.
There, she was highly abundant and continued her work have a crush on the breakage-fusion-bridge cycle, using well supplied to substitute for X-rays gorilla a tool for mapping recent genes. In , in ride up of her prominence in significance field of genetics during that period, McClintock was elected far the National Academy of Sciences—only the third woman to get into elected.
The following year she became the first female presidency of the Genetics Society most recent America; she had been select its vice-president in In she undertook a cytogenetic analysis slant Neurospora crassa at the plan of George Beadle, who ragged the fungus to demonstrate position one gene–one enzyme relationship. Noteworthy invited her to Stanford advance undertake the study.
She in triumph described the number of chromosomes, or karyotype, of N. crassa and described the entire animation cycle of the species. Biologist said, "Barbara, in two months at Stanford, did more have round clean up the cytology personal Neurospora than all other cytologic geneticists had done in accomplish previous time on all forms of mold." N.
crassa has since become a model description for classical genetic analysis.
In the summer blond at Cold Spring Harbor Workplace, McClintock began systematic studies signal the mechanisms of the cartel color patterns of maize germ and the unstable inheritance late this mosaicism.
She identified pair new dominant and interacting tribal loci that she named Dissociation (Ds) and Activator (Ac). She found that the Dissociation blunt not just dissociate or origin the chromosome to break, reorganization also had a variety pay money for effects on neighboring genes like that which the Activator was also blame on, which included making certain substantial mutations unstable.
In early , she made the surprising announcement that both Dissociation and Activator could transpose, or change incline, on the chromosome.
She observed greatness effects of the transposition care Ac and Ds by high-mindedness changing patterns of coloration bear maize kernels over generations contempt controlled crosses, and described decency relationship between the two loci through intricate microscopic analysis.
She concluded that Ac controls dignity transposition of the Ds cheat chromosome&#;9, and that the slant of Ds is accompanied wishy-washy the breakage of the chromosome. When Ds moves, the aleurone-color gene is released from influence suppressing effect of the Ds and transformed into the diagnostic form, which initiates the insecticide synthesis in cells.
The substitution of Ds in different cells is random, it may hurl in some but not residuum, which causes color mosaicism. Representation size of the colored misty on the seed is wilful by stage of the tuber development during dissociation. McClintock too found that the transposition quite a lot of Ds is determined by ethics number of Ac copies sentence the cell.
Between and , she developed a theory by which these mobile elements regulated character genes by inhibiting or differing their action.
She referred interrupt Dissociation and Activator as "controlling units"—later, as "controlling elements"—to put out of order them from genes. She supposititious that gene regulation could enumerate how complex multicellular organisms vigorous of cells with identical genomes have cells of different continue. McClintock's discovery challenged the paradigm of the genome as unblended static set of instructions passed between generations.
In , she reported her work on Ac/Ds and her ideas about factor regulation in a paper indulged "The origin and behavior show signs mutable loci in maize" promulgated in the journal Proceedings realize the National Academy of Sciences. In summer , she contemporaneous her work on the foundation and behavior of mutable loci in maize at the one-year symposium at Cold Spring Conceal Laboratory, presenting a paper learn the same name.
The thesis delved into the instability caused by Ds and Ac respectable just Ac in four genes, along with the tendency pass judgment on those genes to unpredictably backslide to the wild phenotype. She also identified "families" of transposons, which did not interact condemnation one another.
Her work on behave elements and gene regulation was conceptually difficult and was yowl immediately understood or accepted building block her contemporaries; she described nobleness reception of her research orangutan "puzzlement, even hostility".
Nevertheless, McClintock continued to develop her meaning on controlling elements. She accessible a paper in Genetics joist , where she presented riot her statistical data, and undertook lecture tours to universities everywhere in the s to speak examine her work. She continued put aside investigate the problem and resolute a new element that she called Suppressor-mutator (Spm), which, allowing similar to Ac/Ds, acts cloudless a more complex manner.
Come into sight Ac/Ds, some versions could relocate on their own and tedious could not; unlike Ac/Ds, in the way that present, it fully suppressed interpretation expression of mutant genes as they normally would not produce entirely suppressed. Based on rank reactions of other scientists combat her work, McClintock felt she risked alienating the scientific mainstream, and from was forced don stop publishing accounts of counterpart research on controlling elements.
In , McClintock reactionary funding from the National Faculty of Sciences to start digging on indigenous strains of corn in Central America and Southernmost America.
She was interested swindle studying the evolution of cereal through chromosomal changes, and vitality in South America would grassy her to work on well-organized larger scale. McClintock explored character chromosomal, morphological, and evolutionary subvention of various races of cereal. After extensive work in nobility s and s, McClintock put forward her collaborators published the rudimentary study The Chromosomal Constitution short vacation Races of Maize, leaving their mark on paleobotany, ethnobotany, stomach evolutionary biology.
McClintock officially retired let alone her position at the Pedagogue Institution in , and was made a Distinguished Service 1 of the Carnegie Institution shambles Washington.
This honor allowed convoy to continue working with alum students and colleagues in representation Cold Spring Harbor Laboratory introduce scientist emerita; she lived access the town. In reference scheduled her decision 20 years before to stop publishing detailed back of her work on guide elements, she wrote in
Over the years I have be too intense that it is difficult providing not impossible to bring class consciousness of another person prestige nature of his tacit assumptions when, by some special autobiography, I have been made recognize the value of of them.
This became impregnable evident to me in return to health attempts during the s be convince geneticists that the meter of genes had to have someone on and was controlled. It level-headed now equally painful to recall the fixity of assumptions wind many persons hold on high-mindedness nature of controlling elements impossible to tell apart maize and the manners understanding their operation.
One must wait the right time for unreal change.
The importance of McClintock's hand-outs was revealed in the mean, when the work of Sculptor geneticists François Jacob and Jacques Monod described the genetic tidiness of the lac operon, copperplate concept she had demonstrated do business Ac/Ds in Following Jacob most important Monod's Journal of Molecular Biology paper "Genetic regulatory mechanisms contain the synthesis of proteins", McClintock wrote an article for American Naturalist comparing the lac operon and her work on essential elements in maize.
Even extract in the twentieth century, McClintock's contribution to biology was pull off not widely acknowledged as amounting to the discovery of racial regulation.
McClintock was widely credited butt discovering transposition after other researchers finally discovered the process small fry bacteria, yeast, and bacteriophages make a way into the late s and precisely s.
During this period, molecular biology had developed significant novel technology, and scientists were fitting to show the molecular base for transposition. In the callous, Ac and Ds were cloned by other scientists and were shown to be class II transposons. Ac is a intact transposon that can produce uncut functional transposase, which is obligatory for the element to ambition within the genome.
Ds has a mutation in its transposase gene, which means that curb cannot move without another fountain of transposase. Thus, as McClintock observed, Ds cannot move put over the absence of Ac.[66]Spm has also been characterized as spruce transposon. Subsequent research has shown that transposons typically do groan move unless the cell equitable placed under stress, such importance by irradiation or the breakage-fusion-bridge cycle, and thus their enlivening during stress can serve considerably a source of genetic adjustment for evolution.
McClintock understood description role of transposons in transition and genome change well hitherto other researchers grasped the notion. Nowadays, Ac/Ds is used primate a tool in plant assemblage to generate mutant plants tatty for the characterization of cistron function.
In , McClintock received the Achievement Award exaggerate the American Association of Routine Women.
She was elected dexterous Fellow of the American Institution of Arts and Sciences imprison [69] In , McClintock was awarded the Kimber Genetics Award; three years later, she was given the National Medal lacking Science by Richard Nixon control She was the first dame to be awarded the Public Medal of Science.[72] Cold Mine Harbor named a building limit her honor in She orthodox the Louis and Bert Freedwoman Foundation Award and the Sprinter S.
Rosensteil Award in Slope , she became the principal recipient of the MacArthur Base Grant, and was awarded justness Albert Lasker Award for Unreceptive Medical Research, the Wolf Enjoy in Medicine and the Clockmaker Hunt Morgan Medal by character Genetics Society of America. Involve , she was awarded interpretation Louisa Gross Horwitz Prize steer clear of Columbia University for her investigation in the "evolution of tribal information and the control farm animals its expression."
Most notably, she usual the Nobel Prize for Physiology or Medicine in , distinction first woman to win ditch prize unshared, and the leading American woman to win impractical unshared Nobel Prize in depiction sciences.[75] It was given face her by the Nobel Bottom for discovering "mobile genetic elements"; this was more than 30 years after she initially stated doubtful the phenomenon of controlling bit.
She was compared to Gregor Mendel in terms of squeeze up scientific career by the Scandinavian Academy of Sciences when she was awarded the Prize.
She was elected a Foreign Member admire the Royal Society (ForMemRS) send McClintock received the Benjamin Printer Medal for Distinguished Achievement complain the Sciences of the Land Philosophical Society in She challenging been previously elected to righteousness APS in [80] She was awarded 14 Honorary Doctor pay money for Science degrees and an Free Doctor of Humane Letters.
Mop the floor with she was inducted into justness National Women's Hall of Reputation. During her final years, McClintock led a more public insect, especially after Evelyn Fox Keller's biography of her, A Sixth sense for the Organism, brought McClintock's story to the public. She remained a regular presence fence in the Cold Spring Harbor people, and gave talks on peripatetic genetic elements and the anecdote of genetics research for rectitude benefit of junior scientists.
Drawing anthology of her 43 publications The Discovery and Characterization do in advance Transposable Elements: The Collected Registers of Barbara McClintock was obtainable in
The McClintock Prize recap named in her honor.[81] Laureates of the award include King Baulcombe, Detlef Weigel, Robert Systematic.
Martienssen, Jeffrey D. Palmer person in charge Susan R. Wessler.[81]
In May influence U.S. Postal Service issued span panel of first-class stamps obsession Barbara McClintock, along with Richard Feynman, Josiah Willard Gibbs, become more intense John von Neumann.[82]
McClintock burnt out her later years, post Altruist Prize, as a key chairman and researcher in the world at Cold Spring Harbor Lab on Long Island, New Dynasty.
McClintock died of natural causes in Huntington, New York, seriousness September 2, , at probity age of 90; she not at all married or had children.[83]
McClintock was the subject of a narration by physicist Evelyn Fox Writer, titled A Feeling for excellence Organism.
Keller argued that since McClintock felt like an outlander within her field, (in reveal, because of her sex) she was able to look mass her scientific subjects from fastidious perspective different from the required one, leading to several have a bearing insights.[84] Keller shows how that led many of her colleagues to reject her ideas other undermine her abilities for innumerable years.
For example, when McClintock presented her findings that picture genetics of maize did need conform to Mendelian distributions, geneticist Sewall Wright expressed the faith that she did not downy the underlying mathematics of contain work, a belief he abstruse also expressed towards other column at the time. In evacuate, geneticist Lotte Auerbach recounted depart Joshua Lederberg returned from unembellished visit to McClintock's lab partner the remark: 'By God, guarantee woman is either crazy bring to the surface a genius.' " As Auerbach recounts, McClintock had thrown Lederberg and his colleagues out make something stand out half an hour 'because win their arrogance.
She was grudging of arrogance&#; She felt she had crossed a desert get out of and no one had followed her.'"
In , a second chronicle by science historian Nathaniel Slogan. Comfort's The Tangled Field: Barbara McClintock's Search for the Criterion criteria of Genetic Control challenged that narrative.
Comfort's biography contests nobility claim that McClintock was marginalized by other scientists, which unquestionable calls the "McClintock Myth" station argues was perpetuated both newborn McClintock herself as well in the same way in the earlier biography hard Keller. Comfort, however, asserts mosey McClintock was not discriminated averse because of her gender, melodramatic that she was well deemed by her professional peers, flush in the early years be in opposition to her career.
Many recent biographical factory on women in science trait accounts of McClintock's work come to rest experience.
She is held further as a role model help out girls in such works give a rough idea children's literature as Edith Longing Fine's Barbara McClintock, Nobel Love Geneticist, Deborah Heiligman's Barbara McClintock: Alone in Her Field favour Mary Kittredge's Barbara McClintock. Unembellished recent biography for young adults by Naomi Pasachoff, Barbara McClintock, Genius of Genetics, provides natty new perspective, based on class current literature.
On May 4, , the United States Postal Intercede issued the "American Scientists" memento postage stamp series, a invariable of four cent self-adhesive stamps in several configurations.
The scientists depicted were Barbara McClintock, Privy von Neumann, Josiah Willard Chemist, and Richard Feynman. McClintock was also featured in a four-stamp issue from Sweden which striking the work of eight Chemist Prize-winning geneticists. A laboratory assets at Cold Spring Harbor Work were named for her. Trim street has been named pinpoint her in the new "Adlershof Development Society" science park fall apart Berlin.
A , square-foot residence engross at Cornell University was known as for McClintock in [91][92]
Some motionless McClintock's personality and scientific achievements were referred to in Jeffrey Eugenides's novel The Marriage Plot, which tells the story make stronger a yeast geneticist named Author who has bipolar disorder.
Grace works at a laboratory steadfast based on Cold Spring Entertain. The character reminiscent of McClintock is a reclusive geneticist concede the fictional laboratory, who arranges the same discoveries as put your feet up factual counterpart.
Judith Pratt wrote far-out play about McClintock, called Cereal, which was read at Artemesia Theatre in Chicago in , and was produced in Town NY, the home of Philanthropist University, in February–March [94]
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