The human mitochondrial genome contains 16,569 base pairs.
Human mitochondrial DNA is a small, circular molecule found in mitochondria rather than in the cell nucleus. The reference human mitochondrial sequence, known as the Cambridge Reference Sequence, is 16,569 base pairs long and contains 37 genes: 13 protein-coding genes, 22 transfer-RNA genes, and two ribosomal-RNA genes.
Mitochondrial DNA is unusually compact, with little noncoding sequence compared with nuclear chromosomes. It helps encode components of the mitochondrial machinery used in oxidative phosphorylation, but most mitochondrial proteins are encoded by nuclear DNA.
Mitochondria are generally inherited through the egg, so mitochondrial variants often show maternal inheritance. This is different from saying that every mitochondrial trait is exclusively maternal; nuclear genes also control many mitochondrial functions.