Variability of nucleotides, amino acids, and hydropathy across the mitochondrial genome. The sequence is of the concatenated protein-coding genes and the bar at top indicates the limits of each gene. The sequence for ND6 is the reverse complement to maintain a consistent reading frame. Plots are the mean values for all 36 vertebrate taxa with a sliding window of 10 for amino acids and third-position nucleotides or 20 for (combined) first- and second-position nucleotides.