A transcription unit is defined by three regions in DNA as

Options

A. Promoter, terminator and inducer
B. Promoter, structural gene and terminator
C. Inducer, Structural gene and Operator
D. Promoter, Operator and Structural gene

Answer

To answer the question regarding the components of a transcription unit in DNA, we can break down the solution as follows:

### Step-by-Step Solution:

1. **Definition of a Transcription Unit**:
- A transcription unit is a segment of DNA that is transcribed into RNA. It is essential for the process of transcription, where the DNA sequence is converted into an RNA sequence.

2. **Components of a Transcription Unit**:
- There are three main components that define a transcription unit:
- **Promoter**: This is the region of DNA where the transcription process begins. It serves as the binding site for RNA polymerase, the enzyme responsible for synthesizing RNA from the DNA template.
- **Structural Gene**: This is the part of the transcription unit that is actually transcribed into RNA. It contains the coding sequence that will be translated into a protein.
- **Terminator**: This is the sequence of DNA that signals the end of transcription. Once RNA polymerase reaches this region, it detaches from the DNA, and the newly synthesized RNA molecule is released.

3. **Identifying the Correct Answer**:
- Based on the components discussed, we can evaluate the options provided in the question. The correct option must include the three components: promoter, structural gene, and terminator.
- The options given include:
- Option 1: Promoter, Terminator, Inducer (Inducer is not part of the transcription unit)
- Option 2: Promoter, Structural Gene, Terminator (This is correct)
- Option 3: Promoter, Inducer, Structural Gene (Inducer is not part of the transcription unit)
- Option 4: Promoter, Operator, Structural Gene (Operator is not part of the transcription unit)
- Therefore, the correct answer is **Option 2: Promoter, Structural Gene, Terminator**.