FIGURE 5.

Regulatory elements in development, differentiation or evolution. (A) At an initial stage in development, differentiation or evolution, the genome has a silenced gene and a regulatory element located in a distance from it (regulatory element 1, depicted with a green circle). (B) The original “early” regulatory element interacts with its target gene in order to activate it. (C) At subsequent developmental, differentiation or evolutional stages, the genome could develop new regulatory elements (regulatory elements 2 and 3, depicted with orange and red circle, respectively) between the gene and its original “early” regulatory element, which interact with their target gene. (D) At some cases, at later developmental, differentiation or evolutional stages, we could observe a new regulatory element (regulatory element 4, depicted with a yellow circle) outside the original “early” loop, which could also interact with its target gene via a formation of a new loop.