Operator of operon is the target for the attachment of

Options

A. Inducer substance
B. Repressor protein
C. RNA polymerase
D. Repressor gene

Answer

**Step-by-Step Solution:**

1. **Understanding the Operon Concept**: The operon is a functional unit of genomic DNA containing a cluster of genes under the control of a single promoter. It is primarily found in prokaryotes, such as bacteria.

2. **Identifying the Components of an Operon**: An operon typically consists of three main components:
- The promoter, where RNA polymerase binds to initiate transcription.
- The operator, which is a segment of DNA that acts as a regulatory switch.
- Structural genes, which are the genes that are transcribed to produce proteins.

3. **Role of the Operator**: The operator is a specific region within the operon that can bind regulatory proteins. The binding of these proteins can either inhibit or promote the transcription of the structural genes.

4. **Repressor Protein**: The repressor protein is a type of regulatory protein that can bind to the operator region. When the repressor is bound to the operator, it prevents RNA polymerase from transcribing the downstream genes, effectively blocking gene expression.

5. **Conclusion**: Based on the understanding of the operon structure and the role of the operator, we can conclude that the operator of an operon is the target for the attachment of a repressor protein.

**Final Answer**: The operator of the operon is the target for the attachment of **repressor protein** (Option B).

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