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Some of our finest [ about ] Approved Articles Developed Articles (over 800) Share your knowledge. It's a way to achieve immortality. —Often attributed to the Dalai Lama Article of the Week [ about ] Three-dimensional model of the structure of part of a DNA double helix. Deoxyribonucleic acid (DNA) is a very large biological molecule that is vital in providing information for the development and reproduction of living things. Every living organism has its own DNA sequence that is like a unique 'barcode' or 'fingerprint'. This inheritable variation in DNA is the most important factor driving evolutionary change over many generations. But, beyond these general characteristics, what "exactly" is DNA? What are the precise physical attributes of this molecule that make its role so centrally imposing in understanding life? DNA is a long polymer of simple units called nucleotides, held together by a sugar phosphate backbone. Attached to each sugar molecule is a molecule of one of four bases; adenine (A), thymine (T), guanine (G) or cytosine (C), and the order of these bases on the DNA strand encodes information. In most organisms, DNA is a double-helix (or duplex molecule) consisting of two DNA strands coiled around each other, and held together by hydrogen bonds between bases. Because of the chemical nature of these bases, adenine always pairs with thymine and guanine always pairs with cytosine. This complementarity forms the basis of semi-conservative DNA replication — it makes it possible for DNA to be copied relatively simply, while accurately preserving its information content. [more...] New Draft of the Week [ about ] The International Olympic Committee was established in order to deal with the increasing problem of doping in the sports world and follows three fundamental principals, protecting the health of athletes, respecting medical and sports ethics, and ensuring equality for all athletes. The list of drugs banned from the Olympics is determined by the World Anti-Doping Agency. The banned substances and techniques fall into the following categories: androgenic agents, blood doping, peptide hormones, stimulants, diuretics, narcotics and cannabinoids. The use of alcohol (ethanol) is banned in selected sports only during actual competition. [more...]