AA and CG dinucleotides in the human genome. Positional autocorrelation of AA and CG dinucleotides in the complete human genome. The normalized histograms of occurrences of the dinucleotide pairs at distances 2-80 bases from one another are shown. The histograms are smoothed by running average of 3 positions. Level 1.0 corresponds to average scores of the respective raw histograms (3.29 × 107 for AA and 6.38 × 105 for CG). Two peaks on the CG curve (arrowheads, at positions 31 and 62) correspond to 10.4 × 3 base distances between CG dinucleotides in Alu sequences (see text). Vertical grid lines indicate the 10.4 base nucleosome DNA period.