Watson and Crick, DNA

Jeltsch A. Beyond Watson and Crick DNA methylation and molecular enzy-mology of DNA methyltransferases. Chem Biochem 2002 3 274—293. 

As has been well known since the pioneering experiments of Griffith, Avery, MacLeod, McCarty, Watson, and Crick, DNA is the genetic material of bacterial and mammalian cells. DNA encodes information in a triplet code which specifies the sequence of amino acids in proteins. Proteins are the enzymatic and structural polymers of cells. DNA consists of two antiparallel chains of nucleotides. Hydrogen bonds between bases on one strand and bases on the opposite strand constitute in the aggregate sufficient bond... 

DNA Structure From Mendel s Garden to Watson and Crick DNA Structure Variations on a Theme... 

Since the discovery of the double helix structure by Watson and Crick, DNA has been the most important substance in molecular biology. DNA consists of base, sugar, and phosphoric acid. There are four kinds of base in natural DNA, adenine (A), cytosine (C), guanine (G), and thymine (T) as shown in Scheme 25.1. 

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. 

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. 

Watson and Crick showed that the normal structure of DNA consists of a double helix made from two single oligonucleotide strands. The two sugar-phosphate strands of the helix run in opposite (anti-parallel) directions and the bases point... 

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