Operator (biology)

In genetics, an operator is a segment of DNA to which a transcription factor protein binds. It is classically defined in the lac operon as a segment between the promoter and the genes of the operon. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes. An inducer (protein) can displace a repressor (protein) from the operator site (DNA), which results in an uninhibited operon.