noun, plural: promoters
In the Operon Model, the promoter is the gene segment that serves as the initiation site where RNA polymerase binds to and initiates the transcription of certain genes. Conversely, in the presence of a repressor protein, this segment binds with the repressor. Because of this, the RNA polymerase cannot bind to it, resulting in the prevention of transcription of genes. And, this segment is now referred to as the operator gene.
Word origin: promote » Middle English promoten, from Old French promoter, from Latin prōmovēre, prōmōt- : prō-, forward + -er.