Deoxyribonucleic acid Watson-Crick model

James D. Watson (1928-) and Francis H. C. Crick (1916- ) publish two landmark papers in the journal Nature. The papers are entitled Molecular structure of nucleic acids a structure for deoxyribose nucleic acid and Genetic implications of the structure of deoxyribonucleic acid. Watson and Crick propose a double helical model for DNA and call attention to the genetic implications of their model. Their model is based, in part, on the x-ray crystallographic work of Rosalind Franklin (1920-1958) and the biochemical work of Erwin Chargaff (1905- ). Their model explains how the genetic material is transmitted. 

According to the Watson-Crick model, two helically arranged chains are wound around each other to produce a double helix in double-strand deoxyribonucleic acids (Figure 29-2). The double helix rotates upward in a clockwise direction (P-helix). The screwlike rotation of the strands causes periodically recurring large and small furrows to occur at 2.2 or 1.2 nm. Thus, after 3.4 nm or ten base pairs, a complete rotation has occurred. The double helix diameter is about 2 nm. 

Secondary Structure of Deoxyribonucleic Acid. Watson and Crick have developed a model on the basis of X-ray data obtained by Wilkins, which has been substantiated by other analyses. 

DNA (deoxyribonucleic acid) A nucleic acid, mainly found in the chromosomes, that contains the hereditary information of organisms. The molecule is made up of two antiparallel helical polynucleotide chains coiled around each other to give a double helix. It is also known as the Watson-Crick model after James Watson and Francis Crick who first proposed this model in 1953. Phosphate molecules alternate with... 

Crick (1954) proposed a two-stranded helix, somewhat reminiscent of the Watson-Crick double-strand helix which had been so successful for deoxyribonucleic acid. The model consisted of two polypeptide chains wound helically around a common axis and held together by interchain peptide hydrogen bonds. The peptide bonds were all in the cfs-configuration, and the repeating unit consisted of a pair of amino acid residues, one perpendicular and the other parallel to the fiber axis. As a result, planes... 

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