Gene expression, where cells use the genetic information encoded in DNA to produce proteins, has been thought of as a dimmer light.

How much a particular gene gets expressed continually rises and falls, depending on the needs of a cell at any given time. It’s like adjusting the lighting of a room until it’s just right for your mood.

But University at Buffalo researchers have shown that a considerable portion of a human’s roughly 20,000 genes express more like your standard light switch—fully on or fully off.