Random collision frequencies in gene-rich and gene-desert regions. (a) Experimental data obtained for mouse gene-rich regions (shown in separate graphs in Figure 1b) have been plotted into a single graph. A few data points at separation distances above 150 kb, which were omitted in Figure 1b, are included. Statistical analyses were performed on the floating mean (red squares) as explained in Figure 1b. The dashed lines delimit supranucleosomal domains (D.I to D.VI) that encompass separation distances where random collision frequencies are alternatively lower and higher: 0 to 35 kb (domain I), 35 to 70 kb (domain II), 70 to 115 kb (domain III), 115 to 160 kb (domain IV), 160 to 205 kb (domain V) and 205 to 250 kb (domain VI). (b) Random collision frequencies were determined by 3C-qPCR at four sites (R9, F25, F35 and F48; Figure 1) located in an AT-rich/gene-desert region located on mouse chromosome 11. Red squares represent the floating mean (20-kb windows, shift of 10 kb). Error bars are standard error of the mean (the triple asterisks indicate a P-value < 0.01).