Ratio of TF arrival times for switches and barriers. Here we show the density plot of the difference in arrival to the two target sites for (A) and (B) switches (overlapping sites by 5 bp) and (C), (D), (E) and (F) barriers (distances ⁠). We considered an overlap of 5 bp because it is the average overlap between two adjacent binding sites; see Figure 1A. We simulated facilitated diffusion in (A–D), but only 3D diffusion in (E) and (F). The set of parameters for the TFs performing facilitated diffusion are listed in Supplementary Table S2, while the set of parameters for the system TFs performing only 3D diffusion are listed in Supplementary Table S3. In (A), (C) and (E) the two TF species have the same abundance (10 molecules), while in (B), (D) and (F) the second TF is 10 times more abundant than the first TF (⁠ and ⁠). Note that in (D) to emphasize the dependence of the arrival time on the distance we also plot the case of overlapping binding sites.