regulatory sequence

A regulatory sequence is a control panel written into the DNA itself. It does not code for a protein; instead it is a stretch of DNA that proteins read and bind to in order to govern when, where, and how strongly nearby genes are expressed.

This is an umbrella term. Promoters mark where transcription begins; enhancers crank it up, sometimes from far away; silencers turn it down; operators in bacteria provide a docking site for a repressor. Each works by offering a sequence that particular regulatory proteins recognise, so the local mix of bound proteins sets the gene's output.

Much of the genome that does not code for proteins is in fact regulatory, and variation in these sequences explains a great deal of the natural difference between individuals. Because a regulatory change can shift a gene's expression without altering the protein it makes, such variants are an important and often subtle contributor to traits and to disease.