Scientists » Geneticists » BARBARA MCCLINTOCK
|Full name||: Barbara McClintock|
|Alias||: Barbara McClintock|
|Education||: 1927 - Cornell University Erasmus Hall High School Cornell University College of Agriculture and Life Sciences|
Barbara McClintock was a renowned American scientist who did pioneering work in the field of cytogenetics. Her theories on gene regulation and discovery of “jumping genes” were a major breakthrough for the scientific world. An inquisitive soul since her childhood days, she was also a highly independent personality and that was probably one of the reasons her name was changed to Barbara from Eleanor; the latter being considered a very feminine name by her parents. The young child had a strained relationship with her mother who insisted that Barbara shouldn’t be admitted to college but eventually at his father’s insistence she was admitted to college. It was during college that she realised her interest in genetics and embarked on a life long journey in the stream. Always engrossed in solving some or the other problem this eminent scientist made some path breaking advancements in her chosen field. Starting from devising a technique to observe the chromosome in maize to charting the first gene map, to making detailed analysis on the life cycle of the species Neurospora crassa, her achievements are innumerable. But her most significant contribution was her theory on genetic regulation which even earned her a Nobel Prize. The dedicated cytogeneticist devoted her entire life towards scientific advancement and died a solitary soul. Read on to know more about her contributions to the sphere of genetics
The budding scientist continued her study of chromosomal behaviour in maize during meiosis and devised a technique, using carmine staining, which allowed researchers to observe chromosomes under the microscopes.
In the years 1930-31, she made a major breakthrough by explaining the concept of chromosomal cross-over as observed in homologous chromosomes during meiosis. Along with botanist Harriet Creighton she established scientific proof of the hypothesis that chromosomal cross over was responsible recombination of genetic traits.
The duo published a paper titled ‘A Correlation of Cytological and Genetical Crossing-over in Zea mays’ explaining their works.
Also in 1931, she created the first ever genetic map for maize representing the arrangement of three genes on maize chromosome 9. In further expansion of their work on chromosomal crossover, they demonstrated that the phenomenon occurs not only in homologous chromosomes but is also evident in sister chromatids.
She then worked in association with Lewis Stadler in Missouri during 1931-32 and used X-rays as mutagen for her studies on genetics. She studied the effects of radiation on chromosomal behaviour and explained the arrangement of DNA sequence on chromosome 6 of maize which is necessary for formation of a nucleolus.
Barbara then studied the non-homologous recombination of genetic material in 1933.She also surmised from her research work with chromosomes that telomeres are the structures that are responsible for maintaining stability of chromosomes during meiosis.
After obtaining a fellowship from the prestigious ‘Guggenheim Foundation’ she worked with Richard B. Goldschmidt in Germany. With growing political unrest in the European continent she had to cut short her six week training, during 1933-34.
From 1934-36, she continued her research work at ‘Cornell University’ which was funded by a grant from the ‘Rockefeller Foundation’.
In 1936, she joined the ‘University of Missouri’ as an Assistant Professor in Botany. Two years later she made a breakthrough, in the field of cytogenetics, when she charted the structure and functionality of the genetic loci of the chromosomes, namely centromeres.
Dissatisfied with the management at Missouri, in 1941, McClintock started looking for a job elsewhere. She was then appointed as a visiting faculty at ‘Columbia University’. Later in the same year she joined the ‘Carnegie Institution’ in Washington. She pursued her research in genetics at the ‘Cold Spring Harbor Laboratory’ at the institute.
This eminent cytogeneticist accepted an invitation to Stanford in 1944 where she made extensive karyotypic studies on the species Neurospora crassa and also its life cycle. The same year she became the third woman to be inducted into the ‘National Academy of Sciences’ and was also named the President of ‘Genetics Society of America’.
Back at the ‘Cold Spring Harbor Laboratory’ the same year, she continued her studies on maize and explained the impact of the ‘Dissociator’ (Ds) and ‘Activator’ (Ac) genetic loci, on the phenomenon of genetic mutation.
During the years 1948-50, she made startling revelations regarding the genetic behaviour and propounded the theory of gene regulation. The ‘Dissociator’ (Ds) and ‘Activator’ (Ac) units, which she discovered could exchange their positions on the chromosomes, were the “controlling elements” that influenced the behaviour of genes.
Her extensive research on Ac/Ds were presented in the paper ‘The origin and behavior of mutable loci in maize’ published by the National Academy of Sciences in their journal in 1950. She argued that it was the controlled regulation of the genes by the Ac/Ds units, which leads to formation of functionally and structurally different cells in multicellular organisms.
In 1951, she extended her studies to analyse the behaviour of Dc and As units on the phenotypic traits of four genes in maize and presented her inferences in a paper at the annual conference of the ‘Cold Spring Harbor Laboratory’.
Though her theories were not accepted widely among the scientific community, she remained unfazed by the criticism and continued her research and in 1953 published a paper on Genetics which delved into the theories she had developed, based on the analysis and investigation.
Though she pursued her research work on the Ac/Ds units she refrained from making her inferences public, owing to the reaction of her contemporaries towards her theories. A grant awarded by the National Academy of Sciences in 1957 provided the much needed boost to this scientist and she embarked on a new project which involved the study of progression of the chromosomal changes in maize.
Throughout the next two decades Barbara remained involved in the research work in Central America and during the extensive investigation she also delved into ethnobotany and paleobotany. The findings of the exhaustive research work were compiled together and published as ‘The Chromosomal Constitution of Races of Maize’.
In the 1960s, her discoveries of transposition and gene regulation received the due appreciation when other scientists also arrived at same conclusion through independent studies. With significant technological advancements made in the field of molecular biology it became possible to explain the molecular basis for transposition.
In 1967, she was named scientist emeritus at the ‘Carnegie Institute of Washington’ after her tenure as a researcher ended at the institute. She worked with graduate students and was a ‘Distinguished Service Member of the Carnegie Institution of Washington’.
Towards the later years of her career, this eminent cytogeneticist spent most of her time involved in research at the ‘Cold Spring Harbor Laboratory’ in Long Island, New York.
Barbara McClintock has made many significant contributions in the sphere of cytogenetics but her work on the controlling units and gene regulation paved way for many future discoveries. The revolutionary discoveries regarding the transposable elements on the DNA which lead to genetic mutation, earned her a Nobel Prize in Medicine or Physiology.
On June 16, 1902, Eleanor McClintock aka Barbara McClintock, was born to parents Thomas Henry and Sara Handy McClintock in the capital city of Connecticut.
Eleanor who was rechristened as Barbara spent most of her early childhood with her relatives in New York, as her father a practising physician toiled to establish his business. In 1908, she was enrolled at the ‘Erasmus Hall High School’ when the family shifted base to Brooklyn.
The inquisitive and independent kid realised her attraction towards science and pursued higher education at the ‘Cornell University’, after completing high school in 1919.
At the ‘College of Agriculture’, affiliated to the ‘Cornell University’ she made her first tryst with genetics. Encouraged by eminent botanist Claude B. Hutchinson she took up the subject as a discipline, after earning a bachelor’s degree in Botany in 1923.
Two years later she completed her post-graduation and was awarded an MA in Botany. For her doctoral dissertation she involved in research work involving the structure and functionality of chromosomes in maize. She worked on her thesis under the guidance of botanists Lowell Fitz Randolph and Lester W. Sharp and was awarded a Ph.D. in 1927.
Barbara dedicated her entire life to her work and never married. She breathed her last on September 2, 1992, in New York.
The outstanding scientist is the eponym for a laboratory in Carnegie University of Wahington and a street in a science park in Berlin.
In 1970, this eminent scientist was presented the ‘National Medal of Science’ by the President of United States for her contribution in the field of biology.
The ‘Genetics Society of America’ awarded her the ‘Thomas Hunt Morgan Medal’ in the year 1981. The following year Barbara was honoured by the ‘Columbia University’ with the ‘Louisa Gross Horwitz Prize’ for Biology or Biochemistry.
The distinguished was awarded the Nobel Prize in the category of Medicine or Physiology in the year 1983.