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Encyclopedia > François Jacob

François Jacob (June 17, 1920 Nancy, France -- ) is a French biologist, who together with Jacques Monod, originated the idea that control of enzyme levels in all cells happens through feedback on transcription. June 17 is the 168th day of the year in the Gregorian calendar (169th in leap years), with 197 days remaining. ... 1920 is a leap year starting on Thursday (link will take you to calendar) Events January January 7 - Forces of Russian White admiral Kolchak surrender in Krasnoyarsk. ... This article is about the city in France named Nancy. ... A biologist is a scientist devoted to and producing results in biology through the study of organisms. ... Jacques Lucien Monod (February 9, 1910 - May 31, 1976) was a biologist and a Nobel Prize Winner in Physiology or Medicine in 1965. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ... Transcription may be one of the following: In linguistics, transcription is the conversion of spoken words into written language. ...


Research

In around 1961 Jacob and Monod explored the idea that the control of enzyme expression levels in cells is a result of feedback on the transcription of DNA sequences. Their experiments and ideas gave impetus to the emerging field of molecular developmental biology, and of transcriptional regulation in particular. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Gene expression (also protein expression or often simply expression) is the process by which a genes information is converted into the structures and functions of a cell. ... Transcription may be one of the following: In linguistics, transcription is the conversion of spoken words into written language. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) or deoxyribose nucleic acid is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... From Latin ex- + -periri (akin to periculum attempt). ... Developmental biology is the study of the process by which organisms grow and develop. ... Transcriptional regulation is the mechanism that coordinates the expression of DNA with the needs of various life processes such as development, gestation and metabolism. ...


For many years it had been known that bacterial and other cells could respond to external conditions by regulating levels of their key metabolic enzymes, and/or the activity of these enzymes. For instance if a bacterium finds itself in a broth containing lactose, rather than the simpler sugar glucose, it has to adapt itself to the need to 1) import lactose, 2) cleave lactose to its constituents glucose and galactose, and 3) convert the galactose to glucose. It was known that cells ramp up their production of the enzymes that do these steps when exposed to lactose, rather than wastefully producing these enzymes all the time. Studies of enzyme activity control were progressing through theories of the (allosteric) action of small molecules on the enzyme molecule itself (switching it on or off), but how the production of enzymes themselves were controlled was less easy to understand. Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... A metabolic enzyme is an enzyme involved in a metabolic pathway. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Liquid in which meat, fish, cereal grains, or vegetables have been simmered and strained out. ... Lactose is the sugar making up around 2-8% of the solids in milk. ... A space-filling model of glucose Glucose, a simple monosaccharide sugar, is one of the most important carbohydrates and is used as a source of energy in animals and plants. ... Galactose (also called brain sugar) is a type of sugar found in dairy products, in sugar beets and other gums and mucilages. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ...


With the earlier determination of the structure and central importance of DNA, it became clear that all proteins were being produced in some way from its genetic code, and that this step might form a key control point. Jacob and Monod made key experimental and theoretical discoveries that demonstrated that in the case of the lactose system outlined above (in the bacterium E. coli), there are specific proteins that are devoted to repressing the transcription of the DNA to its product (RNA, which in turn is decoded into protein). Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) or deoxyribose nucleic acid is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... Binomial name Escherichia coli T. Escherich, 1885 Escherichia coli (usually abbreviated to E. coli) is one of the main species of bacteria that live in the lower intestines of warm-blooded animals (including birds and mammals) and are necessary for the proper digestion of food. ... Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. ... For other senses of the word code, see code (disambiguation). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


This repressor (the lac repressor) is made in all cells, binds directly to DNA at the genes it controls, and physically prevents the transcription apparatus from gaining access to the DNA. In the presence of lactose, this repressor binds lactose, making it no longer able to bind to DNA, and the transcriptional repression is lifted. In this way, a robust feedback loop is constructed that allows the set of lactose-digesting proteins products to be made only when they are needed. The lac repressor is a DNA-binding protein which stops the metabolism of lactose in bacteria as long as glucose is available. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ...


Jacob and Monod somewhat recklessly extended this repressor model to all genes in all organisms, in their initial exuberance. The fact is that the regulation of gene activity has developed into a very large sub-discipline of molecular biology, and exhibits enormous variety in mechanism and many levels of complexity. Current researchers find regulatory events at every conceivable level of the processes that express genetic information. In the relatively simple genome of baker's yeast, (Saccharomyces cerevisiae), 405 of its 6,419 protein-encoding genes are directly involved in transcriptional control, compared to 1,938 that are enzymes. In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... Molecular biology is the study of biology at a molecular level. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Binomial name Saccharomyces cerevisiae Saccharomyces cerevisiae is a species of budding yeast. ...


Awards and recognition

  • discoveries concerning genetic control of enzyme and virus synthesis.  (http://okilpob.tripod.com/mkdir/jacob-speech.html)
Preceded by:
Jean-Louis Curtis
Seat 38
Académie française
Succeeded by:
Incumbent

 
 

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