Average densities of the motifs in different regions. Densities are measured as no. motifs/Mb in a window of 500 nucleotides. Averages were calculated for all DCC-binding regions (blue), HAS (red) and regions not bound by the complex on the X chromosome (green) and for 4000 randomly sampled regions of the autosomes (1000 per major autosomal arm; in grey). The 500 nucleotides-long windows were slided (one nucleotide at a time and in both directions) from the center of the regions (position indicated as "0" in the X axis), to determine how densities vary when we move away from that center. The broad horizontal grey and black lines indicate the average length of DCC-binding regions and HAS, respectively. All analyses were oriented respect to the positions of the telomeres and centromeres of the chromosomes. Thus, values at the left of the "0" position are obtained when the windows are moved towards the telomere and those at the right, when they are slided towards the centromere.