How do bacteria avoid wasteful production of unnecessary proteins when their genes are always on? The answer lies in regulating the operon. As trp levels increase, trp binds to trpR, causing a ...

The genes lacZ, lacY and lacA are transcribed from a single promoter (P) that produces a single mRNA from which the three proteins are translated. The operon is regulated by Lac repressor, the product ...

The gene lacI, which encodes the lac repressor, LacI, sits outside the operon and is constitutively expressed. A cyclic adenosine monophosphate (cAMP) receptor protein (CRP) binding site (C) sits in ...