The Lac Operon (Jacob & Monod Model)
Polycistronic structural genes regulated by common promoter and operator:
- $z$ gene: Codes for $\beta$-galactosidase (hydrolyses lactose to glucose and galactose).
- $y$ gene: Codes for permease (increases cell permeability to $\beta$-galactosides).
- $a$ gene: Codes for transacetylase.
- In Absence of Inducer: Repressor protein binds to operator, blocking RNA polymerase.
- In Presence of Allolactose (Inducer): Binds to repressor, inactivating it and initiating transcription.
