The DNA double helix is 50 years old!
On Saturday, February 28, 1953, two young scientists, J. Watson and F. Crick, in a small diner Eagle in Cambridge they announced to a crowd of people who came to lunch that they had discovered the secret of life. Many years later, Odile, the wife of F. Crick, said that, of course, she did not believe him: when he came home, he often said something like that, but then it turned out that this was a mistake. This time there was no mistake, and with this statement, a revolution in biology began that continues to this day.
April 25, 1953 in the magazine Nature three articles on the structure of nucleic acids appeared at once. In one of them, written by J. Watson and F. Crick, the structure of the DNA molecule in the form of a double helix was proposed. In two others, written by M. Wilkins, A. Stokes, G. Wilson, R. Franklin and R. Gosling, experimental data were presented confirming the helical structure of DNA molecules. The story of the discovery of the DNA double helix resembles an adventure novel and deserves at least a brief summary.
The most important ideas about the chemical nature of genes and the matrix principle of their reproduction were first clearly formulated in 1927 by N.K. Koltsov (1872–1940). His student N.V. Timofeev-Resovsky (1900–1981) took these ideas and developed them as the principle of convariant reduplication of genetic material. German physicist Max Delbrück (1906–1981; Nobel Prize 1969), active in the mid-1930s At the Kaiser Wilhelm Institute of Chemistry in Berlin, under the influence of Timofeev-Ressovsky, he became so interested in biology that he abandoned physics and became a biologist.
For a long time, in full accordance with the definition of life given by Engels, biologists believed that some special proteins were the hereditary substance. No one thought that nucleic acids could have anything to do with genes - they seemed too simple. This continued until 1944, when a discovery was made that radically changed the entire further development of biology.
This year, Oswald Avery, Colin McLeod and McLean McCarthy published an article stating that in pneumococci, inherited properties are transferred from one bacteria to another using pure DNA, i.e. DNA is the substance of heredity. McCarthy and Avery then showed that treating DNA with a DNA-cleaving enzyme (DNase) causes it to lose the properties of the gene. It is still not clear why this discovery was not awarded the Nobel Prize.
Shortly before that, in 1940, L. Pauling (1901–1994; Nobel Prizes in 1954 and 1962) and M. Delbrück developed the concept of molecular complementarity in antigen-antibody reactions. In the same years, Pauling and R. Corey showed that polypeptide chains can form helical structures, and somewhat later, in 1951, Pauling developed a theory that made it possible to predict the types of X-ray patterns for various helical structures.
After the discovery of Avery et al., despite the fact that it did not convince the supporters of the theory of protein genes, it became clear that it was necessary to determine the structure of DNA. Among those who understood the importance of DNA for biology, a race for results began, accompanied by fierce competition.
X-ray machine used in the 1940s to study the crystal structure of amino acids and peptides
In 1947–1950 E. Chargaff, on the basis of numerous experiments, established the rule of correspondence between nucleotides in DNA: the numbers of purine and pyrimidine bases are the same, and the number of adenine bases is equal to the number of thymine bases, and the number of guanine bases is equal to the number of cytosine bases.
The first structural works (S.Ferberg, 1949, 1952) showed that DNA has a helical structure. Having vast experience in determining the structure of proteins from x-rays, Pauling would no doubt have been able to quickly solve the problem of the structure of DNA, if he had any decent x-rays. However, there were none, and according to what he managed to get, he could not make an unambiguous choice in favor of one of the possible structures. As a result, in his haste to publish the result, Pauling chose the wrong option: in a paper published in early 1953, he proposed a structure in the form of a three-stranded helix, in which phosphate residues form a rigid core, and nitrogenous bases are located on the periphery.
Many years later, recalling the story of the discovery of the structure of DNA, Watson remarked that “Linus [Pauling] did not deserve to guess the right solution. He didn't read the articles and didn't talk to anyone. Moreover, he even forgot his own article with Delbrück, which talks about the complementarity of gene replication. He thought he could figure out the structure just because he was so smart.”
When Watson and Crick began work on the structure of DNA, much was already known. It remained to obtain reliable X-ray structural data and interpret them on the basis of the information already available at that time. How it all happened is well described in the famous book by J. Watson "Double Helix", although many of the facts in it are presented in a very subjective way.
J. Watson and F. Crick on the verge of a great discovery
Of course, in order to build a double helix model, extensive knowledge and intuition were needed. But if there were no coincidence of several accidents, the model could appear several months later, and other scientists could be its authors. Here are some examples.
Rosalind Franklin (1920–1958), who worked with M. Wilkins (Nobel Prize in 1962) at King's College (London), obtained the highest quality DNA X-rays. But this work was of little interest to her, she considered it routine and was in no hurry to draw conclusions. This was facilitated by her bad relationship with Wilkins.
At the very beginning of 1953, Wilkins, without the knowledge of R. Franklin, showed Watson her radiographs. In addition, in February of the same year, Max Perutz showed Watson and Crick the annual report of the Medical Research Council with a review of the work of all leading employees, including R. Franklin. This was enough for F. Crick and J. Watson to understand how the DNA molecule should be arranged.
X-ray of DNA obtained by R. Franklin
In an article by Wilkins et al., published in the same issue Nature, as the article by Watson and Crick, it is shown that, judging by the X-ray patterns, the structure of DNA from different sources is approximately the same and is a helix in which the nitrogenous bases are located inside, and the phosphate residues are outside.
The article by R. Franklin (with her student R. Gosling) was written in February 1953. Already in the initial version of the article, she described the structure of DNA in the form of two coaxial and shifted relative to each other along the axis spirals with nitrogenous bases inside and phosphates outside. According to her, the pitch of the DNA helix in form B (ie, at a relative humidity of >70%) was 3.4 nm, and there were 10 nucleotides per turn. Unlike Watson and Crick, Franklin did not build models. For her, DNA was no more interesting to study than coal and carbon, which she worked on in France before coming to King's College.
When she learned about the Watson-Crick model, she added by hand in the final version of the article: “Thus, our general ideas do not contradict the Watson and Crick model given in the previous article.” Which is not surprising, because. this model was based on her experimental data. But neither Watson nor Crick, in spite of the most friendly relations with R. Franklin, they never told her what, years after her death, they repeated publicly many times - that without her data they would never have been able to build their model.
R. Franklin (far left) at a meeting with colleagues in Paris
R. Franklin died of cancer in 1958. Many believe that if she lived to 1962, Nobel Committee I would have to break my strict rules and give the award to not three, but four scientists. In recognition of her and Wilkins' accomplishments, one of the buildings at King's College was named "Franklin-Wilkins," forever connecting the names of people who barely spoke to each other.
Upon acquaintance with the article by Watson and Crick (it is given below), one is surprised by its small volume and lapidary style. The authors perfectly understood the significance of their discovery and, nevertheless, limited themselves to a description of the model and a brief indication that “from the postulated ... specific pairing, a possible mechanism for copying genetic material immediately follows.” The model itself was taken as if “from the ceiling” - there is no indication of how it was received. Its structural characteristics are not given, except for the pitch and the number of nucleotides per helix pitch. The formation of pairs is also not clearly described, because at that time two systems of numbering of atoms in pyrimidines were used. The article is illustrated with only one drawing made by F. Crick's wife. However, for ordinary biologists, the crystallographically overloaded papers by Wilkins and Franklin were difficult to read, while Watson and Crick's paper was understood by everyone.
Later, both Watson and Crick admitted that they were simply afraid to state all the details in the first article. This was done in a second article entitled "Genetic Implications from the Structure of DNA" and published in Nature May 30 of the same year. It provides justifications for the model, all the dimensions and details of the DNA structure, circuits of chain formation and base pairing, and discusses the various implications for genetics. The nature and tone of the presentation indicate that the authors are quite confident in their correctness and the importance of their discovery. True, they connected the G–C pair with only two hydrogen bonds, but already a year later they indicated in a methodological article that three bonds were possible. Pauling soon confirmed this with calculations.
Watson and Crick's discovery showed that genetic information is written in DNA in a four-letter alphabet. But it took another 20 years to learn how to read it. The question immediately arose as to what genetic code. The answer to it was proposed in 1954 by the theoretical physicist G.A. Gamow *: information in DNA is encoded by triplets of nucleotides - codons. This was confirmed experimentally in 1961 by F. Crick and S. Brenner. Then, within 3–4 years, in the works of M. Nirenberg (Nobel Prize 1965), S. Ochoa (Nobel Prize 1959), H. Korana (Nobel Prize 1965) and others, the correspondence between codons and amino acids.
In the mid 1970s. F. Sanger (b. 1918; Nobel Prizes in 1958 and 1980), who also worked at Cambridge, developed a method for determining nucleotide sequences in DNA. Sanger used it to sequence the 5386 bases that make up the bacteriophage jX174 genome. However, the genome of this phage is a rare exception: it is a single-stranded DNA.
The real era of genomes began in May 1995, when J.K. Venter announced the decoding of the first genome unicellular organism– bacteria haemophilus influenzae. The genomes of about 100 different organisms have now been deciphered.
Until recently, scientists thought that everything in a cell is determined by the sequence of bases in DNA, but life, apparently, is much more complicated.
It is now well known that DNA often has a shape other than the Watson-Crick double helix. More than 20 years ago, the so-called Z-helix structure of DNA was discovered in laboratory experiments. This is also a double helix, but twisted in the opposite direction compared to the classical structure. Until recently, it was believed that Z-DNA is not related to living organisms, but recently a group of researchers from the National Institutes of Heart, Lung and Blood (USA) found that one of the genes of the immune system is activated only when part of its regulatory sequence passes into Z-shape. Now it is assumed that the temporary formation of the Z-form may be a necessary link in the regulation of the expression of many genes. In some cases, viral proteins have been found to bind to Z-DNA and cause cell damage.
In addition to helical structures, DNA can form the well-known twisted rings in prokaryotes and some viruses.
Last year, S. Nidle from the Institute for Cancer Research (London) discovered that the irregular ends of chromosomes - telomeres, which are single strands of DNA - can fold into very regular structures resembling a propeller). Similar structures were found in other parts of the chromosomes and were called G-quadruplexes, since they are formed by DNA regions rich in guanine.
Apparently, such structures contribute to the stabilization of the DNA segments on which they are formed. One of the G-quadruplexes was found directly next to the gene c-MYC, the activation of which causes cancer. In this case, it can prevent gene activator proteins from binding to DNA, and researchers have already started looking for drugs that stabilize the structure of G-quadruplexes, in the hope that they will help in the fight against cancer.
IN last years not only the ability of DNA molecules to form structures other than the classical double helix was discovered. To the surprise of scientists, in the nucleus of a cell, DNA molecules are in continuous motion, as if “dancing”.
It has long been known that DNA forms complexes with histone proteins in the nucleus with protamine in spermatozoa. However, these complexes were considered durable and static. With the help of modern video technology, it was possible to capture the dynamics of these complexes in real time. It turned out that DNA molecules constantly form fleeting bonds with each other and with a variety of proteins that, like flies, hover around DNA. Some proteins move so fast that they travel from one side of the nucleus to the other in 5 seconds. Even histone H1, which is most strongly associated with the DNA molecule, dissociates every minute and binds to it again. This variability of connections helps the cell to regulate the activity of its genes - DNA constantly checks for the presence of transcription factors and other regulatory proteins in its environment.
The nucleus, which was considered a rather static formation - a repository of genetic information - actually lives a stormy life, and the well-being of the cell largely depends on the choreography of its components. Some human diseases can be caused by imbalances in the coordination of these molecular dances.
Obviously, with such an organization of the life of the nucleus, its different parts are not equivalent - the most active "dancers" should be closer to the center, and the least active - to the walls. And so it turned out. For example, in humans, chromosome 18, which has only a few active genes, is always located near the border of the nucleus, and chromosome 19, full of active genes, is always near its center. Moreover, the movement of chromatin and chromosomes, and even just mutual arrangement chromosomes, apparently, affects the activity of their genes. Thus, the proximity of chromosomes 12, 14 and 15 in the nuclei of mouse lymphoma cells is considered a factor contributing to the transformation of the cell into cancer.
The past half century in biology has become the era of DNA - in the 1960s. deciphered the genetic code, in the 1970s. recombinant DNA was obtained and sequencing methods were developed, in the 1980s. polymerase chain reaction (PCR) was developed; in 1990, the Human Genome Project was launched. One of Watson's friends and colleagues, W. Gilbert, believes that the traditional molecular biology died - now everything can be found out by studying the genomes.
F. Crick among the staff of the laboratory of molecular biology in Cambridge
Now, looking at Watson and Crick's papers 50 years ago, one is surprised how many of the assumptions turned out to be true or close to the truth - after all, they had almost no experimental data. As for the authors themselves, both scientists are celebrating the fiftieth anniversary of the discovery of the structure of DNA, now actively working in different fields of biology. J. Watson was one of the initiators of the "Human Genome" project and continues to work in the field of molecular biology, and in early 2003 F. Crick published an article on the nature of consciousness.
J.D. watson,
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* Georgy Antonovich Gamov (1904–1968, emigrated to the USA in 1933) is one of the greatest scientists of the 20th century. He is the author of the theory of theta decay and the tunnel effect in quantum mechanics; liquid-drop model of the atomic nucleus - the basis of the theories of nuclear decay and thermonuclear reactions; theory of the internal structure of stars, which showed that the source of solar energy are thermonuclear reactions; theories " big bang» in the evolution of the Universe; theory of relic radiation in cosmology. His non-fiction books are well known, such as the series of books about Mr. Tompkins ("Mr. Tompkins in Wonderland", "Mr. Tompkins inside himself", etc.), "One, two, three ... infinity", "A planet called Earth " and etc.
English molecular biologist Francis Harry Compton Crick was born in Northampton, the eldest of two sons of Harry Compton Crick, a wealthy shoe manufacturer, and Anna Elizabeth (Wilkins) Crick. 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 Crick's parents moved to London. As a student at Mill Hill School, Crick showed big interest to 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, Crick 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 Erwin Schrödinger's famous book What is Life? Physical Aspects of the Living Cell” (“What Is Life? The Physical Aspects of the Living Cell”), published in 1944. In the book, Schrodinger asks the question: “How can spatio-temporal events occurring in a living organism be explained from the position 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. Hill, Crick received a Medical Research Council fellowship and in 1947 began working at the Strangeway Laboratory in Cambridge. 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. In 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 deoxyribonucleic acid (DNA).
Genetics as a science arose in 1866 when Gregor Mendel formulated the position that "elements", later called genes, determine inheritance physical properties. Three years later, the Swiss biochemist Friedrich Miescher discovered nucleic acid and showed that it is contained in the cell nucleus. At the dawn of a new century, scientists discovered that genes are located on chromosomes, structural elements cell nuclei. In the first half of the XX century. biochemists determined the chemical nature of nucleic acids, and in the 40s. researchers have found that genes are formed from 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.
When Crick began working on his doctoral dissertation at Cambridge, it was already known that nucleic acids are composed of DNA and RNA (ribonucleic acid), each of which is formed by molecules of the monosaccharide group of pentoses (deoxyribose or ribose), phosphate and four nitrogenous bases - adenine, thymine , guanine and cytosine (RNA contains uracil instead of thymine). In 1950, Erwin Chargaff of Columbia University showed that DNA contains equal amounts of these nitrogenous bases. Maurice H.F. Wilkins and his colleague Rosalind Franklin of King's College London conducted X-ray diffraction studies of DNA molecules and concluded that DNA has the shape of a double helix, resembling a spiral staircase.
In 1951, twenty-three-year-old American biologist James D. Watson invited Crick to work at the Cavendish Laboratory. Subsequently, they established close creative contacts. Based on early research by Chargaff, Wilkins, and Franklin, Crick and Watson set out to determine the chemical structure of DNA. Within two years, they developed the spatial structure of the DNA molecule by constructing its model from balls, pieces of wire and cardboard. According to their model, DNA is a double helix consisting of two chains of monosaccharide and phosphate (deoxyribose phosphate) connected by base pairs within the helix, with adenine connected to thymine, and guanine to cytosine, and the bases to each other by hydrogen bonds.
The model allowed other researchers to visualize DNA replication clearly. The two chains of the molecule are separated at 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. In the same year, Crick received his Ph.D. from Cambridge with a dissertation on X-ray diffraction analysis of protein structure. During 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 were 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 into 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; codons are the same in different species.
Crick, Wilkins, and Watson shared the 1962 Nobel Prize in Physiology or Medicine "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.” Engstrom noted that "the deciphering of 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."
In the year of receipt Nobel Prize Crick became head of the biological laboratory at the University of Cambridge and a foreign member of the Council of the Salk Institute in San Diego (California). In 1977, he moved to San Diego, having received an invitation to become a professor. At the Salkovo Institute, Crick conducted research in the field of neuroscience, in particular, he studied the mechanisms of vision and dreams. In 1983, with the English mathematician Graham Mitchison, he proposed that dreams are a side effect of the process by which the human brain is freed from excessive or useless associations accumulated during wakefulness. Scientists have hypothesized that this form of "reverse learning" exists to prevent neural overload.
In Life Itself: Its Origin and Nature (1981), Crick noted the remarkable similarity of all life forms. "With the exception of mitochondria," he wrote, "the genetic code is identical in all living objects currently studied." Referring to discoveries in molecular biology, paleontology and cosmology, he suggested that life on Earth could have originated from microorganisms that were scattered throughout space from another planet; this theory he and his colleague Leslie Orgel called "immediate panspermia".
In 1940 Crick married Ruth Doreen Dodd; they had a son. They divorced in 1947, and two years later Crick married Odile Speed. They had two daughters.
Crick's numerous awards include the Charles Leopold Mayer Prize of the French Academy of Sciences (1961), the American Research Society Science Prize (1962), the Royal Medal (1972), the Royal Society Copley Medal (1976). Crick is an honorary member of the Royal Society of London, the Royal Society of Edinburgh, the Royal Irish Academy, the American Association for the Advancement of Sciences, the American Academy of Arts and Sciences, and the American National Academy of Sciences.
, Physiologist , Medic
Francis Harry Compton Crick is an English molecular biologist and geneticist. Nobel Prize in Physiology or Medicine (1962, jointly with James Dewey Watson and Maurice Wilkinson).
Francis Crick is born June 8, 1916, Northampton, Great Britain, in the family of a successful shoe manufacturer. After the family moved to London, he studied at Mill Hill School, where he showed his abilities in physics, chemistry and mathematics. In 1937, after graduating from University College Oxford, Crick received a bachelor's degree in natural sciences with a thesis on the viscosity of water at high temperatures.
Every time I write a paper on the origin of life, I decide that I will never write another one...
Creek Francis Harry Compton
In 1939, already during the Second World War, Francis Crick began working in the research laboratory of the Naval Department, dealing with deep-sea mines. At the end of the war, while continuing to work in this department, he got acquainted with the book of the prominent Austrian scientist Erwin Schrödinger “What is life? Physical Aspects of the Living Cell (1944), in which spatio-temporal events occurring in a living organism were 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.
On a fellowship from the Medical Research Council, Crick began working at the Strangeway Laboratory in Cambridge in 1947, where 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 famous Cavendish Laboratory in Cambridge, one of the world centers of molecular biology, where, under the guidance of the prominent biochemist Max Ferdinand Perutz, Francis Crick studied the molecular structure of proteins. He was trying to find the chemical basis of genetics, which he suggested could be found in deoxyribonucleic acid (DNA).
Process scientific research deeply intimate: sometimes we ourselves do not know what we are doing.
Creek Francis Harry Compton
In the same period, simultaneously with Crick, other scientists worked in the same area. In 1950, American biologist Erwin Chargaff of Columbia University came to the conclusion that DNA contains equal amounts of four nitrogenous bases - adenine, thymine, guanine and cytosine. Crick's English colleagues M. Wilkins and R. Franklin from King's College, London University conducted X-ray diffraction studies of DNA molecules.
In 1951, F. Crick began joint research with the young American biologist J. Watson at the Cavendish Laboratory. Building on the early work of Chargaff, Wilkins, and Franklin, Crick and Watson spent two years developing the spatial structure of the DNA molecule, constructing a model of it from balls, pieces of wire, and cardboard. According to their DNA model
In the nucleotide sequence of DNA, genetic information is recorded (encoded) about all the features of the species and the characteristics of the individual (individual) - its genotype. DNA regulates the biosynthesis of components of cells and tissues, determines the activity of the organism throughout its life. is a double helix consisting of two chains of monosaccharide and phosphate connected by base pairs inside the helix, with adenine connected to thymine, and guanine to cytosine, and the bases to each other by hydrogen bonds. The Watson-Crick model allowed other researchers to visualize the process of DNA synthesis clearly. The two chains of the molecule are separated at 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 they completed the DNA model and Francis Crick was awarded a PhD from Cambridge with a dissertation on X-ray diffraction analysis of protein structure. In 1954, he was engaged in deciphering the genetic code. Initially a theoretician, Crick began, together with S. Brenner, the study of genetic mutations in bacteriophages, viruses that infect bacterial cells.
I can name three areas of science in which there has been very rapid progress. First of all, it is molecular biology and geology, which have received explosive development over the past 15–20 years. The third area is astronomy, in which the most important event was the creation of radio telescopes. It was with their help that it was possible to discover many unforeseen and important phenomena in the Universe, such as pulsars, quasars and "black holes".
Creek Francis Harry Compton
By 1961, three types of ribonucleic acid (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, the sites of protein synthesis in the cytoplasm of the cell. 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, and they are the same in different species.
In 1962, Crick, Wilkins, and Watson were awarded the Nobel Prize "for their discoveries concerning the molecular structure of nucleic acids and their significance for the transmission of information in living systems." In the same year that he received the Nobel Prize, Crick became head of the biological laboratory at the University of Cambridge and a foreign member of the Board of the Salk Institute in San Diego, California. In 1977, after moving to San Diego, Francis Creek turned to research in the field of neuroscience, in particular, the mechanisms of vision and dreams.
In his book "Life as it is: its origin and nature" (1981), the scientist noted the amazing similarity of all life forms. Referring to discoveries in molecular biology, paleontology and cosmology, he suggested that life on Earth could have originated from microorganisms that were scattered throughout space from another planet. He and his colleague L. Orgel called this theory “direct panspermia”.
Creek Francis lived a long life, he died on July 30, 2004, in San Diego, USA, at the age of 88.
During his lifetime, Crick was awarded numerous prizes and awards (Sch. L. Mayer Prize of the French Academy of Sciences, 1961; Scientific Prize of the American Research Society, 1962; Royal Medal, 1972; John Singleton Copley Medal of the Royal Society, 1976).
Francis Crick - quotes
Every time I write a paper on the origin of life, I decide that I will never write another one... 
The process of scientific research is deeply intimate: sometimes we ourselves do not know what we are doing.
I can name three areas of science in which there has been very rapid progress. First of all, it is molecular biology and geology, which have received explosive development over the past 15–20 years. The third area is astronomy, in which the creation of radio telescopes was the most important development. It was with their help that it was possible to discover many unforeseen and important phenomena in the Universe, such as pulsars, quasars and "black holes".
James Dewey Watson is an American biochemist. Born April 6, 1928 in Chicago, Illinois. He was the only child of businessman James D. Watson and Jean (Mitchell) Watson. IN hometown the boy received primary and secondary education. It soon became apparent that James was an unusually gifted child, and he was invited to the radio to participate in the Quiz for Kids program. After only two years of study at high school, Watson received a scholarship in 1943 to study at the experimental four-year college at the University of Chicago, where he developed an interest in the study of ornithology. After graduating from the university in 1947 with a bachelor's degree in natural sciences, he then continued his education at Indiana University Bloomington.
Born in Chicago, Illinois. At the age of 15, he entered the University of Chicago, graduating four years later. In 1950, he received his doctorate from the University of Indiana for the study of viruses. By this time, Watson became interested in genetics and began studying in Indiana under the guidance of a specialist in this field, G.D. Meller and bacteriologist S. Luria. In 1950, the young scientist received his Ph.D. for a dissertation on the effect of X-rays on the reproduction of bacteriophages (viruses that infect bacteria). 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, which geneticists spoke so enthusiastically about. His visit to the Cavendish Laboratory in 1951 led to a collaboration with Francis Crick that culminated in the discovery of the structure of DNA.
In October 1951, the scientist went to the Cavendish Laboratory of the University of Cambridge to study the spatial structure of proteins together with D.K. Kendrew. There he met Crick, a physicist who was interested in biology and was writing his doctoral dissertation at that time.
“It was intellectual love at first sight,” argues one historian of science. – Their scientific views and interests are the most important problem, which must be solved if you are a biologist. Despite the commonality of interests, views on life and style of thinking, Watson and Crick criticized each other mercilessly, albeit politely. Their roles in this intellectual duet were different. “Francis was the brain and I was the feeling,” says Watson.
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.
Recalling the attitude towards DNA of the vast majority of biologists of those days, Watson wrote: “After Avery's experiments, it seemed that DNA was the main genetic material. So the clarification chemical structure DNA could be an important step towards understanding how genes reproduce. But unlike proteins, there was very little definite chemical knowledge about DNA. Few chemists have done it, and apart from the fact that nucleic acids are very large molecules built from smaller building blocks, nucleotides, there was nothing known about their chemistry that a geneticist could grasp. Moreover, the organic chemists who worked with DNA were almost never interested in genetics.”
American scientists have tried to bring together all the information so far available about DNA, both physicochemical and biological. As V.N. Soyfer: “Watson and Crick analyzed the data of X-ray diffraction analysis of DNA, compared them with the results of chemical studies of the ratio of nucleotides in DNA (Chargaff's rules) and applied to DNA the idea of L. Pauling about the possibility of the existence of helical polymers, expressed by him in relation to proteins. As a result, they were able to propose a hypothesis about the structure of DNA, according to which DNA was represented by two polynucleotide strands connected by hydrogen bonds and mutually twisted relative to each other. Watson and Crick's hypothesis explained most of the mysteries about the functioning of DNA as a genetic matrix so simply that it was literally immediately accepted by geneticists and experimentally proven in a short time.
Based on this, Watson and Crick proposed the following DNA model:
1. Two strands in the DNA structure are twisted one around the other and form a right-handed helix.
2. Each chain is composed of regularly repeating residues of phosphoric acid and deoxyribose sugar. Nitrogenous bases are attached to sugar residues (one for each sugar residue).
3. The chains are fixed relative to each other by hydrogen bonds connecting nitrogenous bases in pairs. As a result, it turns out that phosphorus and carbohydrate residues are located on the outer side of the helix, and the bases are enclosed inside it. The bases are perpendicular to the axis of the chains.
4. There is a selection rule for pairing bases. A purine base can combine with a pyrimidine, and, moreover, thymine can only combine with adenine, and guanine with cytosine ...
5. You can swap: a) the participants of this pair; b) any pair to another pair, and this will not lead to a violation of the structure, although it will decisively affect its biological activity.
“Our structure,” wrote Watson and Crick, “is thus composed of two chains, each of which is complementary to the other.”
In February 1953, Crick and Watson reported on the structure of DNA. A month later, they created a three-dimensional model of the DNA molecule, made from balloons, pieces of cardboard and wire.
Watson wrote about the discovery to his boss Delbrück, who wrote to Niels Bohr: “Amazing things are happening in biology. It seems to me that Jim Watson made a discovery comparable to what Rutherford did in 1911." It is worth recalling that in 1911 Rutherford discovered the atomic nucleus.
The model allowed other researchers to visualize DNA replication clearly. The two chains of the molecule are separated at 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.
The structure of DNA proposed by Watson and Crick perfectly satisfied the main criterion that was necessary for a molecule to be a repository of hereditary information. “The backbone of our model is highly ordered, and the sequence of base pairs is the only property that can ensure the transfer of genetic information,” they wrote.
Crick and Watson completed the DNA model in 1953, and nine years later, together with Wilkins, they received the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and their importance for the transmission of information in living systems." Wilkins (Maurice Wilkins), - his experiments with X-ray diffraction helped to establish the double-stranded structure of DNA. Rosalind Franklin (1920-58), whose contribution to the discovery of the structure of DNA, according to many, was very significant, was not awarded the Nobel Prize, because she did not live to see this time.
Summarizing data on physical and chemical properties DNA and analyzing the results of M. Wilkins and R. Franklin on X-ray scattering on DNA crystals, J. Watson and F. Crick in 1953 built a model of the three-dimensional structure of this molecule. Critical importance had their proposed principle of chain complementarity in a double-stranded molecule. J. Watson owns the hypothesis of a semi-conservative mechanism of DNA replication. In 1958-1959. J. Watson and A. Tisier carried out studies of bacterial ribosomes that have become classic. The work of the scientist on the study of the structure of viruses is also known. In 1989-1992 J. Watson headed the international scientific program "Human Genome".
Watson and Crick discovered the structure of deoxyribonucleic acid (DNA), the substance that contains all of the genetic information.
By the 1950s, it was known that DNA is a large molecule, which consists of thousands of four small molecules interconnected in a line. different types- nucleotides. Scientists also knew that it was DNA that was responsible for storing and inheriting genetic information, similar to a text written in an alphabet of four letters. The spatial structure of this molecule and the mechanisms by which DNA is inherited from cell to cell and from organism to organism remained unknown.
In 1948, Linus Pauling discovered the spatial structure of other macromolecules - proteins and created a model of the structure, called the "alpha helix".
Pauling also believed that DNA is a helix, moreover, consisting of three strands. However, he could not explain either the nature of such a structure or the mechanisms of DNA self-duplication for transmission to daughter cells.
The discovery of the double helix structure occurred after Maurice Wilkins secretly showed Watson and Crick X-ray DNA molecules made by his collaborator Rosalind Franklin. In this picture, they clearly recognized the signs of a spiral and went to the laboratory to check everything on a three-dimensional model.
In the laboratory, it turned out that the workshop did not supply the metal plates necessary for the stereo model, and Watson cut out four types of nucleotide mock-ups from cardboard - guanine (G), cytosine (C), thymine (T) and adenine (A) - and began to lay them out on the table . And then he discovered that adenine combines with thymine, and guanine with cytosine according to the "key-lock" principle. It is in this way that two strands of the DNA helix are connected to each other, that is, opposite thymine from one strand there will always be adenine from the other, and nothing else.
This arrangement made it possible to explain the mechanisms of DNA copying: two strands of the helix diverge, and an exact copy of its former "partner" in the helix is completed from nucleotides to each of them. By the same principle as a positive is printed from a negative in a photograph.
Although Franklin did not support the hypothesis of the helical structure of DNA, it was her pictures that played a decisive role in the discovery of Watson and Crick. Rosalind did not live to see the award that Wilkins, Watson and Crick received.
Obviously, the discovery of the spatial structure of DNA revolutionized the world of science and led to a number of new discoveries, without which it is impossible to imagine not only modern science, but also modern life in general.
In the sixties of the last century, the assumption of Watson and Crick about the mechanism of DNA replication (doubling) was fully confirmed. In addition, it was shown that a special protein, DNA polymerase, takes part in this process.
Around the same time, another important discovery- genetic code. As mentioned above, DNA contains information about everything that is inherited, including the linear structure of every protein in the body. Proteins, like DNA, are long chains of amino acids. There are 20 of these amino acids. Accordingly, it was not clear how the "language" of DNA, which consists of a four-letter alphabet, is translated into the "language" of proteins, which uses 20 "letters".
It turned out that a combination of three DNA nucleotides clearly corresponds to one of the 20 amino acids. And, thus, "written" on DNA is unambiguously translated into protein.
In the seventies, two more important methods appeared, based on the discovery of Watson and Crick. This is sequencing and obtaining recombinant DNA. Sequencing allows you to "read" the sequence of nucleotides in DNA. It is on this method that the entire program "Human Genome" is based.
Obtaining recombinant DNA is otherwise called molecular cloning. The essence of this method is that a fragment containing a specific gene is inserted into the DNA molecule. In this way, for example, bacteria are obtained which contain the gene for human insulin. Insulin obtained in this way is called recombinant. All "genetically modified foods" are created by the same method.
Paradoxically, reproductive cloning, which everyone is talking about now, appeared before the structure of DNA was discovered. It is clear that now scientists conducting such experiments are actively using the results of the discovery of Watson and Crick. But, initially, the method was not based on it.
The next important step in science was the development in the eighties of the polymerase chain reaction. This technology is used to quickly "replicate" the desired DNA fragment and has already found many applications in science, medicine and technology. In medicine, PCR is used to quickly and accurately diagnose viral diseases. If in the mass of DNA obtained from the analysis of the patient, even in a minimal amount, there are genes brought by the virus, then using PCR it is possible to achieve their "multiplication" and then it is easy to identify.
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." Engstrom 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."