THE NUCELIC ACIDS : DNA AND RNA

The nucleic acids found in viruses and all living organisms (microorganisms, plants and animals) carry the genetic informations. A nucleic of three main constituents: (i) a cyclic five carbon sugar, (ii) a purine or pyrimidine base, and (iii) a phosphate. The sugar is ribose or deoxyribose. Based on the types of sugars, the nucleic acids of two types, ribose nucleic acid (RNA) and deoxyribose sugar (DNA). Most of the organisms contain DNA but few phages, and plants and animal viruses contain RNA as genetic material.

Generally, nucleic acids are associated with protein to from nucleoprotein. In 1868, for the first time F. Miescher isolated nucleic acid from white blood cells that was acidic in nature to which he called nuclein. Purine and pyrimidines were isolated by Fischer in 1880. In1881, Zacharis identified nuclein with chromatin. Altaman in 1899 replaced the term nucleic acid and was awarded Nobel prize for demonstrating the presence of two purines (adenine and guanine) and two pyrimidines (thymine and cytosine). During 1910s, P.A. Levene discovered the phosphate and pentose sugar called dexoyribose molecules, in 1943, three American microbiologist, Ostwald Avery, Colin MacLeod and Maclyn McCarty, for the first time presented the evidence that DNA and F.H.C Crick (a British physicist) presented the double helix model of DNA and they were awarded Nobel Prize.