The last step of DNA fingerprinting is
(a) Blotting
(b) Autoradiography
(c) Hybridisation
(d) Isolation of desired DNA

Options

A. Blotting
B. Autoradiography
C. Hybridisation
D. Isolation of desired DNA

Answer

To solve the question regarding the last step of DNA fingerprinting, we can break down the process into clear steps:

### Step-by-Step Solution:

1. **Understanding DNA Fingerprinting**: DNA fingerprinting is a technique used to identify individuals based on their unique DNA profiles. It involves several steps to analyze DNA samples.

2. **Isolation of DNA**: The first step in DNA fingerprinting is the isolation of the desired DNA from the sample. This is crucial as it allows for the extraction of DNA that will be analyzed.

3. **Digestion of DNA**: After isolation, the DNA is digested using restriction endonucleases. These enzymes cut the DNA at specific sequences, resulting in fragments of varying lengths.

4. **Separation of DNA Fragments**: The next step involves separating these DNA fragments using gel electrophoresis. This technique allows the fragments to be sorted based on size, with smaller fragments moving faster through the gel.

5. **Blotting**: Once the fragments are separated, they are transferred (blotted) onto a membrane, typically nitrocellulose or nylon. This step is essential for the subsequent analysis of the DNA fragments.

6. **Hybridization**: After blotting, specific probes are used to hybridize with the DNA fragments. This step helps in identifying the presence of particular sequences within the fragments.

7. **Autoradiography**: The final step of DNA fingerprinting is autoradiography. In this step, the hybridized DNA fragments are visualized, allowing for the identification of specific DNA patterns. This is done using X-ray film or other imaging techniques to detect the labeled probes.

### Conclusion:
Based on the steps outlined, the last step of DNA fingerprinting is **(b) Autoradiography**.

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