The nitrogenous bases in nucleosides and nucleotides, with the exception of adenine and adenosine, undergo enol-keto tautomerism. Studies have shown that the predominant species in solution is the keto form. Examples are uracil and guanine.
DNA is the chemical basis of heredity and may be regarded as the reserve of genetic information. DNA is exclusively responsible for maintaining the identity of different species of organisms over millions of years. A DNA molecule is capable of self duplication during cell division and identical DNA strands are transferred to daughter cells. Another important function of nucleic acids is the protein synthesis in the cell. Actually, the proteins are synthesised by various RNA molecules in the cell but the message for the synthesis of a particular protein is present in DNA.