Operons

Definition

Operons are clusters of genes under the control of a single promoter, allowing for coordinated regulation and expression. They are commonly found in prokaryotic cells, such as bacteria.

5 Must Know Facts For Your Next Test

1. Operons consist of an operator, promoter, and one or more structural genes.
2. The lac operon is a well-studied example that regulates lactose metabolism in E. coli.
3. Operons can be either inducible, like the lac operon, or repressible, like the trp operon.
4. Regulation of operons often involves repressor proteins that bind to the operator to inhibit transcription.
5. Positive control mechanisms can also regulate operons through activator proteins that enhance RNA polymerase binding.

Review Questions

• What components make up an operon?
• How does the lac operon function in the presence and absence of lactose?
• What is the difference between an inducible and a repressible operon?

Related terms

Promoter:

A DNA sequence where RNA polymerase binds to start transcription.

Repressor Protein: A protein that binds to the operator region to block RNA polymerase and inhibit gene transcription.

Inducer:

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