Cis-regulatory element

A cis-regulatory element is a non-coding DNA sequence that controls the transcription of a nearby gene. It is the primary locus of morphological evolution: while protein-coding sequences change slowly and conservatively, cis-regulatory elements evolve rapidly and produce the spatial and temporal changes in gene expression that generate new body plans, patterns, and structures. The modular architecture of cis-regulatory DNA — discrete enhancers, silencers, and insulators that can be added, deleted, or rewired independently — makes it an evolvable control system. Changes in cis-regulation are how Hox genes and other toolkit genes are deployed in new developmental contexts without altering their protein products.