Fig. 16. The human mitochondrial genome based on DNA sequence analysis. The mitochondrial genome encodes several genes unique to mitochondria, including 22 tRNAs, two ribosomal RNAs, and several polypeptides. Not all of the polypeptides in the mitochondria are encoded by the mitochondrial genome. The mitochondrial genome is about 16.5 kb in length and is a covalently closed supercoiled circle. Each of the two strands has its own origin of replication, designated OL and OH. The positions of the genes encoding the 13 polypeptides and the two ribosomal RNAs are indicated on the map.(This sequence is from GenBank #NC_001807 representing the revised Cambridge Reference Sequence. There are more than 90 complete mitochondrial genome sequences in GenBank, including other reference mitochondrial genome sequences from Sweden, Africa, and Japan.)