Editing Operon (section)

== As a unit of transcription ==

An operon contains one or more [[structural gene]]s which are generally transcribed into one [[polycistronic]] [[mRNA]] (a single mRNA molecule that codes for more than one [[protein]]). However, the definition of an operon does not require the mRNA to be polycistronic, though in practice, it usually is.<ref name="Operons in eukaryotes"/> Upstream of the structural genes lies a [[promoter (biology)|promoter]] sequence which provides a site for [[RNA polymerase]] to bind and initiate transcription. Close to the promoter lies a section of DNA called an ''operator''.