The human mitochondrial genome is compact (16,569 bp). Transcription can be initiated from one of two promoters (HSP1, HSP2) on the heavy strand or the single promoter (LSP) on the light strand. All of these promoters are located in the D-loop, a non-coding region acting as the control region. The genome encodes for 22 tRNAs (yellow circles), 2 rRNAs (dark blue) and 13 canonical protein-coding genes (green, NADH: ubiquinone oxidoreductase subunits 1–6; purple, cytochrome b; pink, cytochrome c oxidase subunits I–III; turquoise, ATPases 6 and 8). Humanin (red) sequence is within the 16S rRNA gene and transcribed from the heavy strand.