An operon consists of

Options

A. Structural genes
B. Operator gene
C. Promoter gene
D. All these

Answer

To answer the question "An operon consists of," we will break down the components of an operon step by step.

### Step-by-Step Solution:

1. **Understanding the Definition of an Operon**:
- An operon is a functional unit of genomic DNA that contains a cluster of genes under the control of a single promoter.

2. **Identifying the Components of an Operon**:
- An operon consists of three main components:
- **Promoter**: This is a specific DNA sequence where RNA polymerase binds to initiate transcription of the genes.
- **Operator**: This is a segment of DNA that acts as a regulatory switch. It is the site where a repressor protein can bind, inhibiting transcription.
- **Structural Genes**: These are the genes that are co-regulated by the operon. They encode proteins that are usually involved in a related function.

3. **Analyzing the Options**:
- Option A: Structural gene - This is one of the components of an operon.
- Option B: Operator gene - This is also a component of an operon.
- Option C: Promoter gene - This is another component of an operon.
- Option D: All these - Since all the above components are part of an operon, this option is correct.

4. **Conclusion**:
- Therefore, the correct answer is **Option D: all of these**. An operon consists of structural genes, an operator, and a promoter.