操纵子 J. Monod与F. Jacob The lac operon Repressor perator (c)Induction perator Structural genes Repressor gene Promoter gene Promoter Po acz lacY lacA ac…-P"o- lacZ lacY lacA Repressor DNA Repressor, protein mRNA with inducer lactose(inducer) bound can no longer (b)Repression lactose bind to perator (ir Repr inducer) operator gene Promote ZY,A genes can be Lacz lacY lacA expressed lac mRNA No lactose in cell o" lacz lacY lacA二 repressor protein is RNA ascription Re pressor bound to operator. polymerase protein Z,Y, A genes cant be expressed transcription, ac because mRNA lacz lacY lacA Permease Trans B-galactosidase acetylase操纵子 J. Monod与F. Jacob