Operons are either RNa polymerase cant bind inducible transcription blocked or repressible according Repressor bound the control to operator mechanism. Seventy pia Plac five different operons controlling 250 Inducer structural genes have Active repressor (lactose) been identified for e RNa polymerase binds Inducer bound coli. Both repression to repressor and induction are examples of negative contro since the Transcription mRNA transcript proceeds repressor proteins turn off transcriptionOperons are either inducible or repressible according to the control mechanism. Seventy￾five different operons controlling 250 structural genes have been identified for E. coli. Both repression and induction are examples of negative control since the repressor proteins turn off transcription