Nucleic acid

Nucleic acid, the vital chemical constituents of living things; a class of complex threadlike molecules comprising 2 main types: DNA (deoxyribo-nucleic acid) and RNA (ribonucleic acid). DNA is found almost exclusively in the nucleus of the living cell, where it forms the chief material of the chromosomes. The DNA molecule's ability to duplicate itself (replicate) makes cell reproduction possible; by directing protein synthesis, DNA controls heredity. RNA performs several important tasks connected with protein synthesis, and is found throughout the cell.