[′sər·kyə·lər dē¦äk·sē¦rī‚bō¦nü¦klē·ik ′as·əd] (biochemistry) A single- or double-stranded ring of deoxyribonucleic acid found in certain bacteriophages and in human wart virus. Also known as ring deoxyribonucleic acid.A deoxyribonucleic acid molecule that has no free 5′ or 3′ ends; characteristic of prokaryotes but also found in mitochondria, chloroplasts, and some viral genomes.