Osmosis video - Lac operon

The lac operon is a genetic regulatory sequence found in bacteria that codes for the production of enzymes necessary for lactose metabolism. The operon is controlled by a repressor protein, LacI, which binds to an operator site on the DNA upstream of the genes and prevents their expression. When lactose is present, it binds to LacI and displaces it from the operator site, allowing transcription of the genes to proceed.