The technique helps to isolate desired gene/ DNA fragment for the construction of rDNA is

Options

A. Eastern blotting technique
B. Western blotting technique
C. Southern blotting technique
D. Northern blotting technique

Answer

To answer the question regarding the technique that helps isolate a desired gene or DNA fragment for the construction of recombinant DNA (rDNA), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a technique that isolates a specific gene or DNA fragment necessary for constructing recombinant DNA (rDNA).

2. **Identifying the Techniques**: The options provided are:
- Option 1: Turn blotting technique
- Option 2: Western blotting technique
- Option 3: Southern blotting technique
- Option 4: Northern blotting technique

3. **Analyzing Each Technique**:
- **Turn Blotting Technique**: This is not a recognized technique in molecular biology for isolating DNA.
- **Western Blotting Technique**: This technique is used to detect specific proteins, not DNA fragments.
- **Southern Blotting Technique**: This is a method specifically designed to detect and isolate specific DNA sequences. It involves the use of restriction enzymes to cut DNA and gel electrophoresis to separate the fragments.
- **Northern Blotting Technique**: This technique is used to study RNA, not DNA.

4. **Conclusion**: Based on the analysis, the Southern blotting technique is the correct answer, as it is specifically designed for isolating and detecting DNA fragments.

### Final Answer:
The technique that helps to isolate the desired gene/DNA fragment for the construction of rDNA is the **Southern blotting technique**.

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