Gene expression in prokaryotes is primarily controlled at the RNA transcription level regulatory protein binds operator 4 blocks downstream DNA from being (a) Absence of inducer transcribed (b) Presence of inducer Operator lac operon I P O Z Y A I P O Z Y A Repressor binds to I mRNA operator, preventing transcription of lac operon I mRNA lac mRNA Repressor Inducer B-Galactosidase Permease Trans- acetylase B-isopropyl thingalactose (IPTG) Inducer-repressor Transcription and complex does not translation of bind to operator lac structural genes -OH HOC -CH inducer: 1,6-allolactose CH LOH 39 OH