Figure 3.

Loop conformation in a chromatin fiber modeled by the E2A model. Two fiber parts must (by definition of the interaction radius r_max) come closer together than 35 nm to form a loop. Chromatin loops on small scales play a very important role in gene regulation because enhancer/silencer and promoter regions of the DNA have to be in close proximity to actually work. The length of these loops is typically on the order of a few kilobasepairs, although there are some exceptions; therefore, the loop shown in this figure is a large one with a length of 167 kbp.