Deoxyribonucleic acid. A nucleic acid consisting of deoxyribonucleotides that serves as the repository of genetic information in all cells and some viruses. Structurally, DNA consists of a long repeating chain of deoxyribonucleotides (a strand). However, DNA is often double stranded meaning that two strands engage in complementary base pairing with one another. Under physiological conditions the two strands twist around a common axis to form a "double helix".