Why is it important to understand biological noise in the context of gene expression?
Noise can be looked at as both a problem and an opportunity for a cell. When the biological community has thought about gene regulation in the past, they have thought about how a promoter turns on and off in response to, say, an environmental stress or some need. The view has been that every cell should be identical. But it’s impossible for every cell to be exactly identical, because just like in every other complex system, it has noise. The reason is that many of the key molecules, like mRNA, are present at only a few copies per cell. If you had 1,000 copies of something, you could imagine going from 998 to 999 to 1,000, and it would smoothly change. But when you have only one or two copies of an mRNA that is controlling some major part of the cell, some cells will have zero, some will have one, and some will have two, and these cells will have radically different behaviors. So if a cell doesn’t suddenly want to be switching between on and off, how does it deal with this? How does it
