The DNA Molecule Essay

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The DNA Molecule

In the autumn of 1951, James Watson (left) and Francis Crick (right) started work on unravelling the structure of DNA. It was known at the time that DNA was present in the nucleus of every living cell, and that it had something to do with heridity, but without a knowledge of its structure little more could be understood about how it actually worked. They approached the problem with the same methodology that had been pioneered by Linus Pauling, who after years of exhaustive study had earlier discovered that many proteins exhibited a helical structure. Their task was to devise a structure which would account for all the chemical and X-ray evidence, and at the same time be consistent with all the structural features of
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In April 1953 Watson and Crick published their structure - the now famous double helix. This brilliant accomplishment ranks as one of the most significant discoveries in science because it led the way to an understanding of genetics in terms of the molecules involved. In 1962 they received the Nobel prize for Medicine in recognition of this achievement, along with Maurice Wilkins of Kings College London who had performed the initial X-ray crystallography studies.

A very small section of DNA showing the double helix structure linked by bases, like the rungs on a twisted ladder.

(Click here or on the image to get 3D structure in Molfile format).

(Click here to get an interactive 3D structure in pdb format - requires Chime).

Bases, Nucleotides and Nucleosides
In every living cell there are found nucleoproteins - substances made up of proteins combined with natural polymers, the nucleic acids. Where the backbone of a protein molecule is a polyamide (or polypeptide) chain, the backbone of a nucleic acid molecule is a polyester chain (called a polynucleotide chain). The ester is derived from phosphoric acid (the acid portion) and a sugar (the alcohol portion).

Polynucleotide chain

The sugar is D-ribose, which is in the group of nucleic acids called ribonucleic

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