McClintock, Barbara( The American geneticist, Nobel Prize in Physiology or Medicine, 1983)
Comments for McClintock, Barbara
Biography McClintock, Barbara
genus. June 16, 1902
American geneticist Barbara McClintock was born in Hartford (Conn.) and was the youngest of three daughters doctor Thomas Henry McClintock and his wife, Sarah Hendy. As a child, Barbara, with his aunt and uncle on the father's side spent much time outside the city, in rural Massachusetts, she liked to be in the nature. When she turned 8 years old, the family moved to Flatbush, Brooklyn (New York), said at the time rather village. Her father worked as a doctor in the 'Standard Oil Company', in his duties included the care team members of oil tankers. M a little girl. fond of skating and other sports. Its partners in the game were the boy next door. At the same time she formed persistent habit of reading and thinking in oinochestve.
In 1918, Mr.. M. graduated from Brooklyn High School. Despite resistance from parents who did not want to follow him to school, but finally yielded to it, M. in 1919. was enrolled in Cornell University in Ithaca (New York), where she was going to study biology at the agricultural college.
At the University of M. elected president of the club girls freshmen. Initially, she was actively involved in public life and even played the banjo in a jazz orchestra. But then decided not to join a women's fraternity when she learned that there had not been invited her friend, a Jewish. She began to visit only available for junior students a lecture on genetics and has made such an impression on his teachers, that they offered her a deal with the graduates, although she was much younger than their. In 1923, Mr.. M. received a bachelor's degree and then continued her training at the botanical department, specializing in cytology (the study of cells), genetics and zoology.
. The favorite targets of genetic research have been the fruit fly (Drosophila melanogaster) and corn, or maize (Zea mays)
. Popularity Draw zofily among scientists explain the short cycle of development, high fertility and some characteristic physical features. Maize development cycle is longer, but bright and variegated color of grains and leaves made it a suitable target for genetic research.
When M. studied more in the junior year at the university, staff of agricultural colleges began to take the first steps in the field of genetics. Professor R.A. Emerson engaged in corn genetics and hybrid lines. M. worked with him, she also established a promising professional contacts with two graduate students, George Y. Beadle and Marcus Rhodes, who later became famous geneticists.
In 1924, Mr.. in the preparation of thesis M. developed a method for studying the individual chromosomes of maize under the microscope. This led her to the idea to do a parallel study of chromosomes and phenotype, or physical signs. In the same year she was appointed assistant in the botanical department, and in 1925. received a master's degree. After writing her thesis on the developed method, M. two years later became a doctor of philosophy. Then, from 1927 to 1931, she worked as a teacher of botanical department.
All these years, M. continued to study the morphology of the chromosomes of maize, as well as their correlation with feyotipicheskim manifestation of traits in adult plants. Together with Harriet Creighton M. found that the maize chromosomes exchange genetic material and information at the time of crossing-over of chromosomes in the early stages of meiosis. Meiosis - the process of cell division, which results in the formation of the germ, or reproductive, cells having half the number of chromosomes than the somatic, or tissue, cells. During fertilization, the number of chromosomes is doubled.
Between 1929 and 1931. M. published 9 articles in the biological and genetic journals. In 1931, Mr.. Cornell University was visited by Thomas Hunt Morgan. Research M. made a deep impression on him. He invited her to publish the proceedings in the prestigious journal 'The scientists note of the National Academy of Sciences' ( 'Proceedings of the National Academy of Science'). Her article on the exchange of genetic information in the course of meiosis 'The correlation of cytological and genetic crossing-over in Zea mays' ( 'A Correlation of Cytological and Genetical Crossing Over in Zea mays') appeared in the August issue of the journal in 1931,
. In the same year, M. received a grant from the National Research Council, which enabled her over the next two years to study genetics of maize. It also adopted a research fellow at the department of Morgan at the California Institute of Technology, . worked at Cornell University and the University of Missouri in Columbia, . studying the correlation between X-ray radiation caused by genetic mutations in the chromosomes of maize and phenotypic manifestation of the plant,
. M. determined that the ring chromosome associated with the emergence of variegated color of corn kernels. She also found nucleolar chromosomes included in the biosynthesis of cellular ribosomes - centers of the biosynthesis of cellular proteins.
Guggenheim Foundation grant enabled it to 1933. in the Kaiser Wilhelm Institute in Berlin. But next year, worried about the growth of Nazism, she returned to Cornell, where up to 1936. worked as a researcher in the department at Emerson, and then receives the appointment as assistant professor of botany at the University of Missouri. Realizing that she had little chance of further advancement, M. in 1941. left the university and worked all summer in the biological laboratory of his old friend Marcus Rhodes in Cold Spring Harbor (New York). In the fall she took the offer to become an employee of the Carnegie Institution of Washington at Cold Spring Harbor, where since that time and its studies on the genetics of corn.
40-e gg. been particularly productive for the M. In the winter months, it analyzes the results of experiments conducted the previous summer, and plans tests for the next year. Summer corn growers in the area in front of the Laboratory. Early experiments have put her on the idea of the presence of mobile genetic elements in the chromosomes of maize. Winter 1943/44 r. she plans a program of experiments, hoping for confirmation of his theory. In the summer of 1944. M. observed that the plant-twins have different intensity of the color of leaves: in some bands stained strongly, others weakly. Noting a similar phenomenon in grains cob, she comes to the conclusion that one of the subsidiaries of plant-specific genetic system, which has no other plant. This phenomenon is now called a genetic transposition, and included in the process of genes - transposon, or migratory genes.
The experimental results gave M. opportunity to articulate a model genetic system. It includes two transpoziruyuschih gene: dissociator, called M. Ds-gene, and activator - Al-gene. According to her observations, . genetic system worked as follows: if the Ds-gene is moved to the next section of chromosome with a structural gene (eg, . to the structural gene, . verifying the pattern of alternating stripes on the leaves of corn), . He filed phenotypic expression of the structural gene and stripes on the leaves were pale,
. However, the suppression exerted by the structural gene, was effective only if the Al-gene took place near the two other genes. If the Al-gene moved (transpoziroval) at a remote site, the suppression of the structural gene Ds-gene did not occur and stripes on the leaves were bright. According to the findings of MI, one of the two genes was overwhelming transpoziruyuschih genome, the other shot him an overwhelming effect.
Made M. discovery of transposition in genetic systems and genetic regulation foreshadowed the achievement of bacterial genetics and overtook them at 15 years. This discovery has had far-reaching consequences: for example, through migratory genes could explain how antibiotic resistance is transferred from one bacterial species to another. Model M. also helped to interpret some phenomena, . incompatible with the strict Mendel's laws of heredity, . who claimed, . that phenotypic traits of any two parents will be distributed in the offspring in accordance with the genetic dominance or recessiveness in simple ratios,
. Scheme M. offer an explanation and mechanism of changes in the pattern of colors of corn cobs from early to late stages of development. M. It was also suggested that the rapid emergence of new species of plants or animals may be associated with mobile genetic elements or genes.
In 1950, Mr.. M. presented a report on their research on the genetics of maize and mobile genetic systems at a symposium at Cold Spring Harbor. Due to the fact that the hypothesis of mobile, . transpoziruyuschih genes prejudice then existing in the genetics of the dogma of genes as a stable component of the chromosomes, . its material does not attach great importance to, . and, . perhaps, . and because, . that the speaker was a woman,
. M. just experienced the frustration and the time has ceased to publish the results of their experiments. From 1958 to 1960. She has not conducted research, and has been preparing cytologists of the South American countries, the program suggested by the National Academy of Sciences. By the time she resumed work on the genetics of maize and movable genes, experts in the field of bacterial genetics in bacteria identified regulatory genes that resemble those that M. found in maize.
M. was awarded the Nobel Prize in Physiology or Medicine 1983. transpoziruyuschih for the discovery of genetic systems. More than three decades since, as the work was performed, which is now set ourselves to her credit.
In an interview with his biographer, Evelyn Fox Keller M. expressed its attitude to the work of the following words: 'When you look at these things, they become part of your being. And you forget about me. The main thing - is that you forget about me '. Affirming the characteristics of the members of the Nobel Committee, called it a loner, M. continues to conduct a study on the genetics of corn in his laboratory and in the experimental field at Cold Spring Harbor. She never married.
In addition to the Nobel Prize, M. Kimber has received the award on the genetics of the National Academy of Sciences (1967), . Medal "For scientific achievements' of the National Science Foundation (1970), . Albert Lasker Award for basic medical research (1970), . Wolff Prize in Medicine Israel Fund Wolff (1981), . Prize Louise Gross-Horwitz, Columbia University (1982),
. In 1981. she received a MacArthur Foundation grant. M. - Member of the National Academy of Sciences, the American Society of Naturalists, the American Philosophical Society, Botanical Society of America and the Genetics Society of America. She has honorary degrees from the University of Rochester, Smith College, the University of Missouri, of Yale University, Williams College, New York University.