What is the first step in the Southern Blot technique

Options

A. Denaturation of DNA on the gel for hybridization with specific probe.
B. Production of a group of genetically identical cells.
C. Digestion of DNA by restriction enzyme.
D. Isolation of DNA from a nucleated cell such as the one from the scene of crime.

Answer

### Step-by-Step Text Solution

1. **Understanding Southern Blotting**: Southern blotting is a technique used to identify specific DNA sequences within a complex mixture of DNA. It involves several steps, starting from the isolation of DNA to the final detection of the DNA sequence of interest.

2. **First Step in Southern Blotting**: The very first step in the Southern blot technique is the **isolation of DNA**. This involves extracting DNA from the sample that needs to be analyzed. The sample can be from various sources, such as blood, tissue, or even from a crime scene.

3. **Importance of DNA Isolation**: The isolation of DNA is crucial because it provides the necessary material for subsequent steps in the Southern blotting process. Without properly isolated DNA, the following steps, such as digestion with restriction enzymes and gel electrophoresis, cannot be performed effectively.

4. **Conclusion**: Therefore, the first step in the Southern blot technique is the **isolation of DNA from a nucleated cell**.