Operon

An operon is a group of genes controlled by shared regulatory DNA and transcribed together into one RNA molecule. This arrangement lets cells coordinate the expression of related genes.

Promoter: A DNA sequence where RNA polymerase binds to begin transcription. The operon’s promoter helps initiate transcription of its genes as one RNA molecule.
lac operon: An Escherichia coli operon that enables lactose uptake and metabolism. It demonstrates induction of an operon when lactose is available.
Gene: A DNA sequence that produces a functional RNA or contributes to a functional product. An operon organizes several genes under shared transcriptional control.
Eukaryotic gene expression: The processes that regulate transcription and translation in eukaryotic cells. Most eukaryotic protein-coding genes are transcribed separately rather than in bacterial-style operons.
Operator: A regulatory DNA sequence where proteins bind to influence transcription. Repressors bound at an operator can block transcription across the operon.
trp operon: An Escherichia coli operon that encodes enzymes for tryptophan synthesis. It demonstrates repression when the pathway’s end product is abundant.
RNA polymerase: An enzyme that synthesizes RNA using a DNA template. It reads the operon’s DNA and produces its transcript.
Monocistronic mRNA: An RNA molecule containing a coding sequence for one protein. It contrasts with the multi-gene transcript commonly produced by an operon.
Repressor: A protein that binds DNA or another regulatory target to reduce gene expression. Operon repressors switch transcription off by interacting with regulatory DNA.
ara operon: An Escherichia coli gene-regulatory system controlling arabinose metabolism. Its regulation combines activator and repressor effects in response to arabinose.

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Jacques MonodBroader topic: Monod’s work with Jacob established the operon as a unit of coordinated gene regulation.