Which of the following sequence of steps is correct in DNA fingerprinting?

Options

A. Southern blotting, Electrophoresis, Hybridisation, Autoradiography
B. Autoradiography, Electrophoresis, Hybridisation, Southern blotting
C. Electrophoresis, Southern blotting, Hybridisation, Autoradiography
D. Hybridisation, Southern blotting, Electrophoresis, Autoradiography

Answer

To determine the correct sequence of steps in DNA fingerprinting, we can break down the process into the following steps:

### Step-by-Step Solution:

1. **Isolation of DNA**: The first step in DNA fingerprinting is to isolate the DNA from the sample. This can be done using various methods, such as using detergents and enzymes to break down cell membranes and release the DNA.

2. **Fragmentation of DNA**: Once the DNA is isolated, it is then cut into smaller fragments using enzymes called endonucleases. These enzymes recognize specific sequences in the DNA and cut it at those sites.

3. **Gel Electrophoresis**: The fragmented DNA is then subjected to gel electrophoresis. In this step, the DNA fragments are separated based on their size. Smaller fragments move faster through the gel matrix than larger ones, allowing for the separation of the different sized fragments.

4. **Southern Blotting**: After electrophoresis, the separated DNA fragments are transferred from the gel onto a membrane (usually nylon or nitrocellulose) in a process called Southern blotting. This step preserves the arrangement of the DNA fragments for further analysis.

5. **Hybridization**: A labeled probe that is complementary to the specific DNA sequences of interest (such as VNTRs) is then added to the membrane. This probe will hybridize with the target DNA sequences, allowing for their identification.

6. **Autoradiography**: Finally, the membrane is exposed to X-ray film to detect the hybridized probe. The presence of radioactive signals indicates the locations of the DNA fragments that have hybridized with the probe, which can be visualized as bands on the film.

### Conclusion:
The correct sequence of steps in DNA fingerprinting is:
1. Isolation of DNA
2. Fragmentation of DNA
3. Gel Electrophoresis
4. Southern Blotting
5. Hybridization
6. Autoradiography