Crick and Watson

Watson and Crick shared the 1962 Nobel Prize in physiol ogy or medicine with Maurice Wilkins who with Rosalind Franklin was responsible for the X ray crystallographic work... 

Watson and Crick published their work in a pa per entitled A Structure for Deoxyribose Nucleic Acid in the British journal A/ature on April 25 1953 In addition to being one of the most important pa pers of the twentieth century it is also remembered for one brief sentence appearing near the end... 

True to their word Watson and Crick followed up their April 25 paper with another on May 30 This second paper Genetical Implications of the Struc ture of Deoxyribonucleic Acid outlines a mechanism for DNA replication that is still accepted as essentially correct... 

The structure proposed by Watson and Crick was modeled to fit crystallographic data obtained on a sample of the most common form of DNA called B DNA Other forms include A DNA which is similar to but more compact than B DNA and Z DNA which IS a left handed double helix... 

Primary and Secondary Structure. The DNA double helix was first identified by Watson and Crick in 1953 (4). Not only was the Watson-Crick model consistent with the known physical and chemical properties of DNA, but it also suggested how genetic information could be organized and rephcated, thus providing a foundation for modem molecular biology. 

As indicated in Chapter 11, the base pairing in DNA is very specific the purine adenine pairs with the pyrimidine thymine the purine guanine pairs with the pyrimidine cytosine. Further, the A T pair and G C pair have virtually identical dimensions (Figure 12.10). Watson and Crick realized that units of such similarity could serve as spatially invariant substructures to build a polymer whose exterior dimensions would be uniform along its length, regardless of the sequence of bases. 

One of the most thoroughly investigated examples of polymeric biomolecules in regard to the stabilization of ordered structures by hydration are the DNAs. Only shortly after establishing the double-helix model by Watson and Crick 1953 it became clear, that the hydration shell of DNA plays an important role in stabilizing the native conformation. The data obtained by the authors working in this field up until 1977 are reviewed by Hopfinger155>. 

Figure 35-2. A diagrammatic representation of the Watson and Crick modei of the doubie-heiicai structure of the B form of DNA.The horizontai arrow indicates the width of the doubie heiix (20 A), and the verticai arrow indicates the distance spanned by one compiete turn of the doubie heiix (34 A). One turn of B-DNA in-ciudes ten base pairs (bp), so the rise is 3.4 A per bp. The centrai axis of the doubie heiix is indicated by the verticai rod. The short arrows designate the poiarity of the antiparaiiei strands. The major and minor grooves are depicted. (A,adenine C, cytosine G, guanine ...

Since the discovery of the double hehcal structure of deoxyribonucleic acid (DNA) by Watson and Crick in 1953 [1], there has been considerable belief that the canonical right-handed B-DNA may adopt a wide range of different conformations depending on the nucleotide sequences and environmental conditions. This speculation turned out to be a reahty [2-10]. hi hving systems, the conformational flexibility of DNA resides primarily in the polymorphs of the DNA double hehx (including right-handed and left-handed double hehcal DNA) and occurs under various environmental conditions [4j. The main family of DNA forms identified, based on circular dichroic and... 

It is now almost 50 years since the structure of DNA was elucidated by Watson and Crick (1) (Fig. 1). Since then the double helix has become an icon for modern scientific achievement. With the rapid growth of molecular biology and the consequent success of the human genome project (2) we are now firmly in a post-genomic era. However, in spite of, or perhaps because of this, efforts to understand fundamental aspects of metal-ion interactions with DNA continue to be vigorously pursued. 

The central role played by DNA in cellular life guarantees a place of importance for the study of its chemical and physical properties. It did not take long after Watson and Crick described the now iconic double helix structure for a question to arise about the ability of DNA to transport electrical charge. It seemed apparent to the trained eye of the chemist or physicist that the array of neatly stacked aromatic bases might facilitate the movement of an electron (or hole) along the length of the polymer. It is now more than 40 years since the first experimental results were reported, and that question has been answered with certainty. 

It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material (Watson and Crick, 1953). 

The exact nature of the lesion in DNA is unknown, and so is the type of DNA that is attacked. Recent X-ray crystallographic studies, as well as other physicochemical studies, have made it clear that DNA is not simply a polynucleotide, folded as Watson and Crick (106) proposed. There are three main conformational types of DNA they each keep the hydrogen-bonded bases in the center of the helix, but may tilt them by a "propellor twist," may slide them from the center of the helix in the plane of the base pairs, and may vary the amount of rotation from one base pair to the next up the helical axes. 

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