Operon
A set of genes transcribed under the control of an operator gene.
More specifically, an operon is a segment of DNA containing adjacent genes including structural genes, an operator gene, and a regulatory gene.
An operon is thus a functional unit of transcription and genetic regulation.
Operons are found in many prokaryotic organisms (bacteria, viruses and some algae) and have yielded valuable insights into microbial genetics.
See also: Selfish operon