- any of a group of long, linear macromolecules, either DNA or various types of RNA, that carry genetic information directing all cellular functions: composed of linked nucleotides.
- biochem any of a group of complex compounds with a high molecular weight that are vital constituents of all living cellsSee also RNA, DNA
- Any of a group of complex compounds found in all living cells and viruses, composed of purines, pyrimidines, carbohydrates, and phosphoric acid. Nucleic acids in the form of DNA and RNA control cellular function and heredity.
- Any of a group of very large polymeric nucleotides that constitute the genetic material of living cells and viruses and that code for the amino acid sequences of proteins. Nucleic acids consist of either one or two long chains of repeating units called nucleotides, which consist of a nitrogen base (a purine or pyrimidine) attached to a sugar phosphate. The two main nucleic acids are DNA and RNA. In DNA, the nitrogen bases along the length of one chain are linked to complementary bases in the other chain by hydrogen bonds, and both chains coil around each other in a double helix. Particular sequences of nucleotides constitute genes and encode instructions for sequences of amino acids when proteins are synthesized. In RNA, which is usually single-stranded, complementary bases within the single strand may pair with each other, forming structures other than a double helix. See more at DNA RNA.