The bacterial genes are usually found in operons. Each operon comprises regulatory sequences of DNA that function as binding sites for regulatory proteins, which inhibit or encourage transcription. The regulatory proteins usually combine with small molecules that can make the protein inactive or active by altering its tendency to combine with DNA.
The four combinations of active or inactive regulatory proteins, which could be observed at any time in the cell are:
1. Active repressor, active activator,
2. Active repressor, inactive activator
3. Inactive repressor, active activator
4. Inactive repressor, inactive activator