1. A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions.
DNA, which consists of a polysugar-phosphate backbone possessing projections of Purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). (online-medical-dictionary.org)
3. A nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses). (Wikipedia.com)
Also known as DNA.