Now, any given unit, any given operon itself also is found next to a regulatory gene. And the regulatory gene basically consists of the sequence of DNA that codes for the repressor or activator. So every single opera next to the opera contains the regulatory gene that codes for either the repressor or the activator that is involved within that opera. Now, to gain more intuition and understanding to what the opera is and how it actually works let's take a look at one particular example of the lack of an opera known as the Lac Operon which stands for the Lactose opera. This is the opera that is used by certain type of prokaryotic cell known as E. Coli. So prokaryotic cells basically control the genes by using the change in concentration of certain types of biological molecules.