![]() ![]() James Watson directed the Human Genome Project at the National Institutes of Health. Other advances in molecular biology stemming from the discovery of the DNA double helix eventually led to ways to sequence genes. Francis Crick played an integral role in both the theory and analysis of the experiments that led to an improved understanding of the genetic code. The details of how sequences of DNA instruct cells to make specific proteins was worked out by molecular biologists during the period from 1953 to 1965. From the DNA double helix model, it was clear that there must be some correspondence between the linear sequences of nucleotides in DNA molecules to the linear sequences of amino acids in proteins. In some way, the genetic molecule, DNA, had to contain instructions for how to make the thousands of proteins found in cells. Structurally, proteins are long chains of amino acid subunits. ![]() When Watson and Crick produced their double helix model of DNA, it was known that most of the specialized features of the many different life forms on Earth are made possible by proteins. Watson and Crick used many aluminium templates like this one, which is the single base Adenine (A), to build a physical model of DNA in 1953. Each strand could then be used as a template for assembly of a new base-pair complementary strand. Just pull apart the two sugar-phosphate backbones, each with its hydrogen bonded A, T, G, and C components. Indeed, the base-pairing did suggest a way to copy a DNA molecule. After realizing the structural similarity of the A:T and C:G pairs, Watson and Crick soon produced their double helix model of DNA with the hydrogen bonds at the core of the helix providing a way to unzip the two complementary strands for easy replication: the last key requirement for a likely model of the genetic molecule. The base pairs are held together by hydrogen bonds, a type of chemical attraction that is easy to break and easy to reform. In particular, the length of each base pair is the same and they fit equally between the two sugar-phosphate backbones. The A:T and C:G pairs are structurally similar. In DNA, the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. The "specific pairing" is a key feature of the Watson and Crick model of DNA, the pairing of nucleotide subunits. ![]() The two base-pair complementary chains of the DNA molecule allow replication of the genetic instructions. Ĭrick, Watson, and Maurice Wilkins who won the Nobel Prize for Medicine in recognition of their discovery of the DNA double helix.ĭNA replication. Delbruck's efforts to promote the " Phage Group" (exploring genetics by way of the viruses that infect bacteria) was important in the early development of molecular biology in general and the development of Watson's scientific interests in particular. Delbruck's thinking about the physical basis of life stimulated Erwin Schrödinger to write, What Is Life? Schrödinger's book was an important influence on Crick and Watson. ![]() Max Delbrück was a physicist who recognized some of the biological implications of quantum physics. Both Crick, and particularly Watson, thought that they were racing against Pauling to discover the structure of DNA. In early 1953, Pauling published a triple helix model of DNA, which subsequently turned out to be incorrect. In 1951, Pauling published the structure of the alpha helix, a fundamentally important structural component of proteins. Linus Pauling was a chemist who was very influential in developing an understanding of the structure of biological molecules. The discovery of the DNA double helix made clear that genes are functionally defined parts of DNA molecules, and that there must be a way for cells to translate the information in DNA to specific amino acids, which make proteins. The application of physics and chemistry to biological problems led to the development of molecular biology, which is particularly concerned with the flow and consequences of biological information from DNA to proteins. The discovery had a major impact on biology, particularly in the field of genetics, enabling later researchers to understand the genetic code. The article presents a simple and elegant solution, which surprised many biologists at the time who believed that DNA transmission was going to be more difficult to deduce and understand. This mystery was the question of how it is possible that genetic instructions are held inside organisms and how they are passed from generation to generation. This article is often termed a "pearl" of science because it is brief and contains the answer to a fundamental mystery about living organisms. Diagramatic representation of the key structural features of the DNA double helix. ![]()
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