Watson and Francis Crick

Early diffraction photographs of such DNA fibers taken by Rosalind Franklin and Maurice Wilkins in London and interpreted by James Watson and Francis Crick in Cambridge revealed two types of DNA structures A-DNA and B-DNA. The B-DNA form is obtained when DNA is fully hydrated as it is in vivo. A-DNA is obtained under dehydrated nonphysiological conditions. Improvements in the methods for the chemical synthesis of DNA have recently made it possible to study crystals of short DNA molecules of any selected sequence. These studies have essentially confirmed the refined fiber diffraction models for A- and B-DNA and in addition have given details of small structural variations for different DNA sequences. Furthermore, a new structural form of DNA, called Z-DNA, has been discovered. 

In 1953, James Watson and Francis Crick made their classic proposal for the secondary structure of DNA. According to the Watson-Crick model, DNA under physiological conditions consists of two polynucleotide strands, running in opposite directions and coiled around each other in a double helix like the handrails on a spiral staircase. The two strands are complementary rather than identical and are held together by hydrogen bonds between specific pairs of... 

The secondary structure of DNA is shown in Figure B. This "double helix" model was first proposed in 1953 by James Watson and Francis Crick, who used the x-ray crystallographic data of Rosalind Franklin and Maurice Wilkins. Beyond that, they were intrigued by the results of analyses that showed that in DNA the ratio of adenine to thymine molecules is almost exactly 1 1, as is the ratio of cytosine to guanine ... 

By now the stage was set for the discoveiy of the three-dimensional structure of DNA, the so-called secondary structure of the molecule. Some of the best minds in science were working on the problem. In 1953, James D. Watson and Francis Crick of Cambridge University announced that they had discovered the structure of DNA. 

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

In the version of evolutionary theory popularised by Dawkins (1976), the fundamental unit of life is a gene, a conceptual abstraction clothed in the biochemistry of the nucleic acid DNA. The purpose, or telos, of this gene is replication - to make copies of itself - copies which because of random chemical and physical processes maybe more or less accurate. The particular chemical structure of DNA provides a mechanism whereby such faithful copying can readily occur - as James Watson and Francis Crick pointed out... 

In 1953, James Watson and Francis Crick (Figure 9) suggested a structure for deoxyribose nucleic acid (DNA). The suggestion had important novel features. One was that it had two helical chains, each coiling around the same axis but having opposite direction. The two helices going in opposite direction, and thus complementing each other, is a simple consequence of the twofold symmetry of the whole double... 

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. 

James Watson and Francis Crick publish paper describing the structure of DNA... 

Double helix—The shape of DNA molecules, discovered by James Watson and Francis Crick. The double helix is made up of two chains of DNA bound to each other by weak chemical bonds between pairs of complementary bases. This base pairing allows the DNA to be copied precisely when the strands separate as cells divide. 

Modern genetics started with the elucidation of the double-helical structure of the DNA molecule by James Watson and Francis Crick in 1953 [20]. It was already known... 

Two major discoveries in 1953 were of crucial importance in the history of biochemistry. In that year James D. Watson and Francis Crick deduced the double-helical structure of DNA and proposed a structural basis for its precise replication (Chapter 8). Their proposal illuminated the molecular reality behind the idea of a gene. In that same year, Frederick Sanger worked out the sequence of amino acid residues in the polypeptide chains of the hormone insulin (Fig. 3-24), surprising many researchers who had long thought that elucidation of the amino acid sequence of a polypeptide would be a hopelessly difficult task. It quickly became evident that the nucleotide sequence in DNA and the amino acid sequence in proteins were somehow related. Barely a decade after these discoveries, the role of the nucleotide... 

Today s understanding of information pathways has arisen from the convergence of genetics, physics, and chemistry in modern biochemistry. This was epitomized by the discovery of the double-helical structure of DNA, postulated by James Watson and Francis Crick in 1953 (see Fig. 8-15). Genetic theory contributed the concept of coding by genes. Physics permitted the determination of molecular structure by x-ray diffraction analysis. Chemistry revealed the composition of DNA. The profound impact of the Watson-Crick hypothesis arose from its ability to account for a wide range of observations derived from studies in these diverse disciplines. 

Within the DNA double helix, the hydrogen-bonded pairs are of a very specific type termed Watson-Crick base pairs (after James Watson and Francis Crick who first described the structure of... 

Described in 1953 by James Watson and Francis Crick, the double helix of DNA (deoxyribonucleic acid) is the cellular storehouse of genetic information. This biopolymer consists of a pair of complementary chains approximately 2.4 nanometers (9.5XlO-8 inches) in diameter and composed of... 

Tautomerism in the bases commands interesting prominence in the history of the elaboration of the structure of DNA by James Watson and Francis Crick. When in the early 1950s Watson was attempting to identify structurally compatible base pairing schemes using simple two-dimensional cardboard models of the bases, he inadvertently deployed the rare tautomeric states until the chemist Jerry Donahue pointed out this error to him. 

The existence of specific base-pairing interactions was discovered in the course of studies directed at determining the three-dimensional structure of DNA. Maurice Wilkins and Rosalind Franklin obtained x-ray diffraction photographs of fibers of DNA (Figure 5.10). The characteristics of these diffraction patterns indicated that DNA was formed of two chains that wound in a regular helical structure. From these and other data, James Watson and Francis Crick inferred a structural model for DNA that accounted for the diffraction pattern and was also the source of some remarkable insights into the functional properties of nucleic acids (Figure 511). 

In 1953 James Watson and Francis Crick proposed a model for the structure of the DNA molecule, based on data about the size and function of the molecule. They built a physical model of their proposed structure in order to help them understand how the molecule functions. Their proposed structure, which consisted of a double helix of two complementary polymer chains, enabled them to predict how DNA replicates. 

James Watson and Francis Crick put together these two pieces of information in their famous 1953 proposal of a double-helix structure for DNA. They concluded that DNA consists of two interacting helical strands of nucleic acid polymer (Fig. 23.24), with each cytosine on one strand linked through hydrogen bonds to a guanine on the other and each adenine to a thymine. This accounted for the observed molar ratios of the bases, and it also provided a model for the replication of the molecule, which is crucial for passing on information during the... 

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