noun, plural: regulatory genes
A gene that is involved in the production of a substance that controls or regulates the expression of one or more genes, such as the gene that codes for a repressor protein that inhibits the activity of an operator gene.
In the Operon Model, the regulatory genes are those that code for the production of regulatory proteins. For instance, the regulatory gene in lac operon is the lac I gene that codes for the lac repressor.
The repressor protein binds to operator gene, which consequently prevents the production of a specific enzyme. When that enzyme is needed again, a specific regulatory metabolite inhibits the repressor so that the enzyme is produced.