Which of the following is not required in the preparation of a recombinant DNA molecule ?

Options

A. Restriction endonuclease
B. DNA ligase
C. DNA fragments
D. E.coil

Explanation

To determine which of the following options is not required in the preparation of a recombinant DNA molecule, we will analyze each option step by step.

### Step 1: Understand the components needed for recombinant DNA preparation
Recombinant DNA technology involves several key components that are essential for the successful creation of recombinant DNA. These components typically include restriction endonucleases, DNA ligases, DNA fragments, and a suitable host organism.

### Step 2: Analyze each option
1. **Restriction Endonucleases**:
- These enzymes are crucial for cutting DNA at specific sequences. They allow scientists to isolate the desired DNA fragments from a larger DNA molecule.
- **Conclusion**: Required for recombinant DNA preparation.

2. **DNA Ligase**:
- This enzyme is responsible for joining the DNA fragments together after they have been cut by restriction endonucleases. It facilitates the formation of phosphodiester bonds between the fragments.
- **Conclusion**: Required for recombinant DNA preparation.

3. **DNA Fragments**:
- These are the pieces of DNA that are to be combined to form the recombinant DNA. Without these fragments, there would be nothing to recombine.
- **Conclusion**: Required for recombinant DNA preparation.

4. **E. coli**:
- E. coli is a bacterium commonly used as a host organism for cloning and expressing recombinant DNA. While it plays a crucial role in the propagation and expression of recombinant DNA, it is not directly involved in the actual preparation of the recombinant DNA molecule itself.
- **Conclusion**: Not required for the preparation of recombinant DNA.

### Step 3: Identify the correct answer
Based on the analysis, the option that is not required in the preparation of a recombinant DNA molecule is **E. coli** (Option D).

### Final Answer
The correct answer is **E. coli** (Option D).

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