[‚mīd·ə¦kän·drē·əl dē¦äk·sē‚rī·bō·nü′klē·ik ′as·əd] (biochemistry) The circular deoxyribonucleic acid duplex, generally 5 to 10 copies, contained within a mitochondrion and maternally inherited since only the egg cell contributes significant numbers of mitochondria to the zygote. Abbreviated mtDNA. Also known as mitochondrial genome.