Question

Can you think for how long the lac operon would be expressed in the presence of lactose?

Answer 1

Part 1: Introduction to Lac operon
Lac operon is a cluster of genes present next to each other involved in the metabolism of lactose in E.coli.

Part 2: Explanation
The Lac operon consists of the control elements and three structural genes where gene Z codes for beta-galactosidase, gene Y codes permease, and gene A codes for transacetylase. Beta- galactosidase, permease and transacetylase are enzymes that are required for lactose metabolism.

But these enzymes are required only until lactose is present in the system. In the absence of lactose, the transcription and translation of the structural genes is not required. Thus the Lac operon regulates the gene expression based on the presence or absence of lactose.

Therefore Lac operon will express until there is lactose available in the system for its metabolism.