I😍🧬🔬🌿🐾🐡🐞🐒🐸🌊🍫🍦🏃 on Instagram: "#control of gene expression #school #review #DNA The regulator gene codes for the repressor, in the case of the lac operon the repressor automatically binds to the operator. This is typical for prokaryotic catabolic reactions like coding for lactose digesting enzymes. The repressor blocks the ability for RNA polymerase to bind to the promoter (this is OK because there is no lactose and these genes are not needed to be transcribed). If lactose is present