Which of the following is next step after hybridisation in DNA finger printing?

Options

A. GEL electrophoresis
B. PCR
C. Autoradiography
D. Southern blotting

Answer

To solve the question regarding the next step after hybridization in DNA fingerprinting, we can break down the process into a series of steps. Here’s a detailed explanation:

### Step-by-Step Solution:

1. **Isolation of DNA**: The first step in DNA fingerprinting is to isolate the DNA from the sample. This involves breaking down the cell membranes and extracting the DNA.

2. **Digestion of DNA by Restriction Endonuclease**: The isolated DNA is then cut into smaller fragments using restriction enzymes. These enzymes recognize specific sequences in the DNA and cut it at those sites.

3. **Separation of DNA Fragments**: After digestion, the DNA fragments are separated based on their size. This is typically done using gel electrophoresis, where an electric current is applied to move the fragments through a gel matrix.

4. **Electrophoresis**: This step involves applying an electric field to the gel containing the DNA fragments. The smaller fragments move faster and further than the larger ones, resulting in a distinct pattern of bands.

5. **Transferring or Blotting**: The separated DNA fragments are then transferred onto a membrane in a process known as blotting (specifically Southern blotting for DNA). This allows for the fragments to be immobilized for further analysis.

6. **Hybridization Using VNTR Probes**: In this step, specific probes (often labeled with a fluorescent or radioactive tag) are used to hybridize with the DNA fragments on the membrane. These probes are designed to bind to variable number tandem repeats (VNTRs) in the DNA.

7. **Detection of Hybrid DNA by Autoradiography**: The final step after hybridization is the detection of the hybridized DNA. This is done using autoradiography, where the membrane is exposed to X-ray film or a similar medium to visualize the locations of the hybridized probes.

### Conclusion:
After hybridization, the next step in DNA fingerprinting is **detection of hybrid DNA by autoradiography**.