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MOST IMPORTANT SCIENTIFIC DISCOVERIES
DNA. History and essence of scientific discovery
Directory / The most important scientific discoveries Genetics as a science arose in 1866, when Gregor Mendel formulated the position that "elements", later called genes, determine the inheritance of physical properties. Three years later, the Swiss biochemist Friedrich Miescher discovered nucleic acid and showed that it is contained in the cell nucleus. On the threshold of a new century, scientists discovered that genes are located in chromosomes, the structural elements of the cell nucleus. In the first half of the XNUMXth century, biochemists determined the chemical nature of nucleic acids, and in the forties, researchers discovered that genes are formed by one of these acids, DNA. It has been proven that genes, or DNA, direct the biosynthesis (or formation) of cellular proteins called enzymes and thus control the biochemical processes in the cell. By 1944, the American biologist Oswald Avery, while working at the Rockefeller Institute for Medical Research, had provided evidence that genes were made up of DNA. This hypothesis was confirmed in 1952 by Alfred Hershey and Martha Chase. Although it was clear that DNA controlled the basic biochemical processes that take place in the cell, neither the structure nor the function of the molecule was known. In the spring of 1951, while attending a symposium in Naples, Watson met Maurice G.F. Wilkins, an English explorer. Wilkins and Rosalynn Franklin, his colleagues at King's College, Cambridge University, performed X-ray diffraction analysis of DNA molecules and showed that they are a double helix, resembling a spiral staircase. The data they obtained led Watson to the idea of investigating the chemical structure of nucleic acids. The National Society for the Study of Infantile Paralysis provided a grant. In October 1951, the scientist went to the Cavendish Laboratory of the University of Cambridge to study the spatial structure of proteins together with John C. Kendrew. There he met Francis Crick, a physicist who was interested in biology and was writing his doctoral dissertation at the time. Subsequently, they established close creative contacts. Starting in 1952, based on the early work of Chargaff, Wilkins, and Franklin, Crick and Watson set out to try to determine the chemical structure of DNA. Francis Harry Compton Creek was born on 8 June 1916 in Northampton, the elder of two sons of Harry Compton Creek, a wealthy shoe manufacturer, and Anna Elizabeth (Wilkins) Creek. After spending his childhood in Northampton, he attended a high school. During the economic crisis that followed the First World War, the family's commercial affairs fell into disrepair, and Francis' parents moved to London. As a student at Mill Hill School, Crick showed great interest in physics, chemistry and mathematics. In 1934 he entered University College London to study physics and graduated three years later with a Bachelor of Science degree. Completing his education at University College, the young scientist considered the viscosity of water at high temperatures; this work was interrupted in 1939 by the outbreak of World War II. During the war years, Creek was engaged in the creation of mines in the research laboratory of the Naval Ministry of Great Britain. For two years after the end of the war, he continued to work in this ministry and it was then that he read the famous book Erwin Schrödinger "What is Life? Physical Aspects of the Living Cell", published in 1944. In the book, Schrödinger asks a question. "How can spatio-temporal events occurring in a living organism be explained from the standpoint of physics and chemistry?" The ideas presented in the book influenced Crick so much that he, intending to study particle physics, switched to biology. With the support of Archibald W. Will, Crick received a Medical Research Council fellowship and began working at the Strangeway Laboratory in Cambridge in 1947. Here he studied biology, organic chemistry, and X-ray diffraction techniques used to determine the spatial structure of molecules. His knowledge of biology expanded significantly after moving in 1949 to the Cavendish Laboratory in Cambridge - one of the world's centers of molecular biology. Under the guidance of Max Perutz, Crick explored the molecular structure of proteins, in connection with which he developed an interest in the genetic code for the sequence of amino acids in protein molecules. About 20 essential amino acids serve as monomeric units from which all proteins are built. Studying what he defined as "the boundary between living and non-living", Crick tried to find the chemical basis of genetics, which, as he suggested, could be laid down in deoxyribo-nucleic acid (DNA). In 1951, twenty-three-year-old American biologist James D. Watson invited Crick to work at the Cavendish Laboratory. James Devay Watson was born April 6, 1928 in Chicago, Illinois to James D. Watson, a businessman, and Jean (Mitchell) Watson, and was their only child. In Chicago, he received his primary and secondary education. It soon became apparent that James was an unusually gifted child, and he was invited to radio to participate in the Quiz for Children program. After only two years in high school, Watson received a scholarship in 1943 to study at an experimental four-year college at the University of Chicago, where he showed interest in the study of ornithology. After earning a Bachelor of Science degree from the University of Chicago in 1947, he continued his education at Indiana University Bloomington. By this time, Watson became interested in genetics and began training in Indiana under the guidance of specialist in this field Herman J. Meller and bacteriologist Salvador Luria. Watson wrote a dissertation on the effect of X-rays on the reproduction of bacteriophages (viruses that infect bacteria) and received his Ph.D. in 1950. A grant from the National Research Society allowed him to continue his research on bacteriophages at the University of Copenhagen in Denmark. There he studied the biochemical properties of bacteriophage DNA. However, as he later recalled, experiments with bacteriophage began to weigh him down, he wanted to know more about the true structure of DNA molecules, about which he was so enthusiastic geneticists said. Crick and Watson knew that there are two types of nucleic acids - DNA and ribonucleic acid (RNA), each of which consists of a monosaccharide of the pentose group, phosphate and four nitrogenous bases: adenine, thymine (in RNA - uracil), guanine and cytosine. Over the next eight months, Watson and Crick summarized their results with those already available, making a report on the structure of DNA in February 1953. A month later, they created a three-dimensional model of the DNA molecule, made of balls, pieces of cardboard and wire. According to the Crick-Watson model, DNA is a double helix, consisting of two chains of deoxyribose phosphate connected by base pairs, similar to the rungs of a ladder. Through hydrogen bonding, adenine combines with thymine, and guanine with cytosine. With this model, it was possible to trace the replication of the DNA molecule itself. The model allowed other researchers to visualize DNA replication clearly. The two strands of the molecule are separated at the sites of hydrogen bonds, like opening a zipper, after which a new one is synthesized on each half of the old DNA molecule. The base sequence acts as a template, or blueprint, for the new molecule. In 1953, Crick and Watson completed the DNA model. This allowed them, along with Wilkins, to share the 1962 Nobel Prize in Physiology or Medicine nine years later "for their discoveries concerning the molecular structure of nucleic acids and their significance for the transmission of information in living systems." A.V. Engström of the Karolinska Institute said at the awards ceremony: "The discovery of the spatial molecular structure ... DNA is extremely important, because it outlines the possibilities for understanding in great detail the general and individual characteristics of all living things." Engström noted that "deciphering the double helix structure of deoxyribonucleic acid with a specific pairing of nitrogenous bases opens up fantastic opportunities for unraveling the details of the control and transmission of genetic information." After the publication of the description of the model in the English magazine "Nature" in April 1953, the tandem of Crick and Watson broke up. In 1965, Watson wrote the book "Molecular Biology of the Gene", which has become one of the most famous and popular textbooks in molecular biology. As for Crick, he received his PhD from Cambridge in 1953 with a dissertation on X-ray diffraction analysis of protein structure. Over the next year, he studied protein structure at the Brooklyn Polytechnic Institute in New York and lectured at various US universities. Returning to Cambridge in 1954, he continued his research at the Cavendish Laboratory, concentrating on deciphering the genetic code. Initially a theoretician, Crick began studying genetic mutations in bacteriophages (viruses that infect bacterial cells) with Sydney Brenner. By 1961, three types of RNA had been discovered: messenger, ribosomal, and transport. Crick and his colleagues proposed a way to read the genetic code. According to Crick's theory, messenger RNA receives genetic information from DNA in the cell nucleus and transfers it to ribosomes (sites of protein synthesis) in the cell's cytoplasm. Transfer RNA carries amino acids into ribosomes. Informational and ribosomal RNA, interacting with each other, provide a combination of amino acids to form protein molecules in the correct sequence. The genetic code is made up of triplets of nitrogenous bases of DNA and RNA for each of the 20 amino acids. Genes are made up of numerous basic triplets, which Crick called codons. Forty years remained before the decoding of the human genome ... Author: Samin D.K.
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