What is the lac operon in E. coli a classic example of?

• A. A positive feedback loop
• B. A repressible operon
• C. An inducible operon
• D. A constitutive operon

Answer: (C)

Verified step by step guidance

1. Understand the concept of an operon: An operon is a cluster of genes under the control of a single promoter and is transcribed into a single mRNA strand. It is a key feature in prokaryotic gene regulation.
2. Learn about the lac operon: The lac operon in E. coli is responsible for the metabolism of lactose. It includes genes that code for proteins involved in the uptake and breakdown of lactose.
3. Identify the type of operon: The lac operon is an inducible operon. This means it is usually off but can be turned on (induced) in the presence of an inducer, which in this case is lactose.
4. Differentiate between inducible and repressible operons: Inducible operons, like the lac operon, are activated by the presence of a specific substrate. Repressible operons, on the other hand, are typically on and can be turned off when a specific product is abundant.
5. Recognize the role of the lac operon as a model: The lac operon is a classic example of an inducible operon because it demonstrates how gene expression can be regulated by environmental factors, specifically the presence or absence of lactose.