Crick-Watson double helix, discovery

Discovery of the Original Crick-Watson Double Helix... 

Biophysicists use a number of physical tools and techniques to understand how cellular processes work, especially at the molecular level. Some of the important tools are electron microscopy, nuclear magnetic resonance (NMR) spectroscopy, circular dichroism (CD) spectroscopy, and X-ray crystallography. For example, the discovery of Watson and Crick s double helix model was possible in part because of the X-ray... 

In 1953, James Watson and Francis Crick determined that the structure of DNA was a double helix. This discovery best helped them —... 

Watson and Crick s discovery of the structure of DNA revolutionized scientists understanding of heredity and genetics. Find out how Watson and Crick showed that the structure of DNA is a double helix. How did Rosalind Franklin s work in X-ray crystallography play a role Present your findings as an annotated, illustrated time line. 

The most famous stracture in aU chemistry is the Watson-Crick double helix for DNA (figure 12.3). The discovery of this structure by James Watson and Francis Crick in 1953 was the beginning of molecular biology. An amazing number of insights about the nature of life have been derived from this structure. 

The Watson-Crick double helix is the outcome of three lines of work. The first is the discovery by Erwin Chargaff of Chargaff s rules." Specifically, for all normal DNAs, A = T, G = C and A + G = C + T. The actual content of each base in DNA varies from species to species over a wide range. Despite this variation, the content... 

In 1962, James Watson, Francis Crick, and Maurice Wilkins won the Nobel Prize in Physiology or Medicine for their discovery that the structure of DNA is a double helix. This double helix is made up of two chains of DNA bound to each other by the ability of each A base to form a weak chemical bond to a T base and each C to a G. The bases only paired with their base partners, so that where one strand had a T, the other had an A, and where one had a C, the other had... 

The experiment was published in 1953 (Miller, 1953), the same year as the discovery of the double helix by Watson and Crick, a memorable year indeed for biochemistry. 

The year 2003 is the tenth anniversary of the first Femtochemistry Conference and the fiftieth anniversary of Watson and Crick s celebrated discovery of the DNA double helix [1], Remarkable progress has been made in both fields femtosecond spectroscopy has made decisive contributions to Chemistry and Biology, and advances in the elucidation of static nucleic acid structures have profoundly transformed the biosciences. However, much less is known about the dynamical properties of these complex macromolecules. This is especially true of the dynamics of the excited electronic states, including their evolution toward the photoproducts that are the end result of DNA photodamage [2],... 

The nucleic acids are among the most complex molecules that you will encounter in your biochemical studies. When the dynamic role that is played by DNA in the life of a cell is realized, the complexity is understandable. It is difficult to comprehend all the structural characteristics that are inherent in the DNA molecules, but most biochemistry students are familiar with the double-helix model of Watson and Crick. The discovery of the double-helical structure of DNA is one of the most significant breakthroughs in our understanding of the chemistry of life. This experiment will introduce you to the basic structural characteristics of the DNA molecule and to the forces that help establish the complementary interactions between the two polynucleotide strands. 

The spectacular discoveries in the area of nucleic acids started with the work of the British scientists Francis Crick, James Watson, and Maurice Wilkins, who were the first to describe the molecular structure of DNA as a double helix made up of two twisted strands. They were jointly awarded the 1962 Nobel Prize for Physiology or Medicine for their discoveries. 

One of the most exciting biological discoveries is the recognition of DNA as a double helix (Watson and Crick, 1953) of two antiparallel polynucleotide chains with the base pairings between A and T, and between G and C (Watson and Crick s DNA structure). Thus, the nucleotide sequence in one chain is complementary to, but not identical to, that in the other chain. The diameter of the double helix measured between phosphorus atoms is 2.0 nm. The pitch is 3.4 nm. There are 10 base pairs per turn. Thus the rise per base pair is 0.34 nm, and bases are stacked in the center of the helix. This form (B form), whose base pairs lie almost normal to the helix axis, is stable under high humidity and is thought to approximate the conformation of most DNA in cells. However, the base pairs in another form (A form) of DNA, which likely occurs in complex with histone, are inclined to the helix axis by about 20° with 11 base pairs per turn. While DNA molecules may exist as straight rods, the two ends bacterial DNA are often covalently joined to form circular DNA molecules, which are frequently supercoiled. 

One of the most important discoveries of modern science was the elucidation of the structures of DNA and RNA as the famous double helix by Watson and Crick in 1953. They realized that the basic structure of base-sugar-phosphate was ideal for a three-dimensional coil. The structure of a small part of DNA is shown opposite. 

During the past half a century, fundamental scientific discoveries have been aided by the symmetry concept. They have played a role in the continuing quest for establishing the system of fundamental particles [7], It is an area where symmetry breaking has played as important a role as symmetry. The most important biological discovery since Darwin s theory of evolution was the double helical structure of the matter of heredity, DNA, by Francis Crick and James D. Watson (Figure 1-2) [8], In addition to the translational symmetry of helices (see, Chapter 8), the molecular structure of deoxyribonucleic acid as a whole has C2 rotational symmetry in accordance with the complementary nature of its two antiparallel strands [9], The discovery of the double helix was as much a chemical discovery as it was important for biology, and lately, for the biomedical sciences. 

At the time Pauling was working on the structure of proteins culminating eventually in his discovery of the alpha-helix. Yet this declaration sounds as if he were anticipating the mechanism of DNA replication via the double helix. It came, however, only in 1953, and it was not Pauling, but Watson and Crick, who discovered it. 

The discovery that DNA from natural sources exists in a double-helical form with Watson-Crick base pairs suggested, but did not prove, that such double helices would form spontaneously outside biological systems. Suppose that two short strands of DNA were chemically synthesized to have complementary sequences so that they could, in principle, form a double helix with Watson—Crick base pairs. Two such sequences are CGAT-TAAT and ATTAATCG. The structures of these molecules in solution can be examined by a variety of techniques. In isolation, each sequence exists almost exclusively as a single-stranded molecule. However, when the two sequences are mixed, a double helix with Watson-Crick base pairs does form (Figure 1.8). T his reaction proceeds nearly to completion. If each of the strands are initially present at equal concentrations of 1 mM, then more than 99.99% of the strands are in the double helix at 25°C and in the presence of 1 M NaCl. 

This statement has a remarkable precedent in the history of the discovery of the DNA double helix Jim Watson and Francis Crick s efforts to build a model of DNA remained futile as long as Jerry Donohue had not told them that they were using the wrong tautomers for the nudeobases (Watson, 1968). 

Read In Search of the Double Helix by John Gribbin, and write a report discussing whether Watson and Crick or Rosalind Franklin really made the discovery of the DNA structure. Include a discussion of how serendipity played a part in the discovery of the structure. 

This paradigm—among many exciting discoveries in basic biomedical research— deserves special attention. We compiled these sources because of their interesting evolving views of the personal and establishment ecosystem dynamics around Crick and Watson and their discovery of the DNA double helix. 

Watson and Crick have each written accounts of their work, and both are weii worth reading. Watson s is entitied The Double Helix. Crick s is What Mad Pursuit A Personal View of Scientific Discovery. 

From the beads-on-a-string linear topology, research moved to the mapping of genes in a chromosome, and later to the discovery that genes were nucleic acids. Their chemical constitution was then determined, first topologically according to the classic structural theory procedures by Todd, and finally in the three-dimensional structural pattern (3D) of the DNA double helix proposed by Watson and Crick in 1953. 

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