Lac operon

Definition

The lac operon is a set of genes found in E. coli and other bacteria that are responsible for the metabolism of lactose. It includes the genes lacZ, lacY, and lacA, which are regulated by a promoter and an operator.

5 Must Know Facts For Your Next Test

1. The lac operon is inducible and is activated in the presence of lactose.
2. LacI is a repressor protein that binds to the operator to block transcription when lactose is absent.
3. Allolactose acts as an inducer by binding to the LacI repressor, causing it to release from the operator.
4. CAP-cAMP complex enhances transcription of the lac operon when glucose levels are low.
5. Mutations in any part of the lac operon can affect its regulation and expression of lactose-metabolizing enzymes.

Review Questions

• What role does allolactose play in the regulation of the lac operon?
• How does glucose availability affect the activation of the lac operon?
• What happens when there is a mutation in the LacI repressor?

Related terms

Promoter:

A DNA sequence where RNA polymerase binds to initiate transcription.

Operator:

A segment of DNA to which a repressor binds, blocking RNA polymerase action.

Inducer:

A molecule that initiates gene expression by disabling a repressor protein.