"Gene regulation is like a pyramid. At the
pyramid's apex are the master regulators, which
control a battery of secondary regulators, which
conerol the final products at the pyramid's base.
That is, some genes cause the synthesis of protein
molecules that control the expression of other
genes, which then cause the synthesis of the
protein molecules that actually make up the cell.
So once a developing cell makes the decision to
switch on a master regulator, that decision deter-
mines everything that happens subsequently "

The linked pdf is an article about brain
development.

"Under normal circumstances, it acts by causing a conformational change in a receptor molecule, which results in a change in the binding affinity of the ligand. In this way, an allosteric ligand modulates the receptor's activation by its primary (orthosteric) ligand, and can be thought to act like a dimmer switch in an electrical circuit, adjusting the intensity of the response."

"In humans, we create our world through language. In organisms, the regulation is like a language, with syntax that operates in specific contexts. "

"In fact, I don't believe there is any "master switch". Cellular regulation is like a chain; you break any link and lots of things go wrong. You can call your favorite "link" a "master switch", but it is self-kidding."

see the link...

"Bad regulation sucks. Over regulation sucks. No regulation sucks too. Regulation is like code. Code bloat is bad but the solution is not "no code." The solution isn't "throw it all out and start again" either. The solution is iterative improvement based on real world feedback and improved transparency. "

"Under normal circumstances, it acts by causing a conformational change in a receptor molecule, which results in a change in the binding affinity of the ligand. In this way, an allosteric ligand modulates the receptor's activation by its primary (orthosteric) ligand, and can be thought to act like a dimmer switch in an electrical circuit, adjusting the intensity of the response."

"systemic osmoregulation is, like many regulatory systems in the body, a negative feedback loop."