Question

What do you understand by DNA fingerprinting technique? Explain its process.

Hint:

VNTRs vary between individuals; the process is: cut → separate → blot → probe → detect.

Answer 1

Step 1: Definition:
DNA fingerprinting is a technique that identifies differences (polymorphisms) in specific repetitive DNA sequences, called VNTRs (variable number of tandem repeats)/satellite DNA, which are unique to each individual (except identical twins). It was developed by Alec Jeffreys.

Step 2: Sample preparation:
DNA is first extracted from a biological sample (blood, hair root, saliva, semen, etc.) and then cut into fragments of varying sizes using restriction endonucleases.

Step 3: Separation and transfer:
The resulting DNA fragments are separated according to size by gel electrophoresis, then transferred and immobilised onto a nylon or nitrocellulose membrane by Southern blotting.

Step 4: Detection:
The membrane is then hybridised with a labelled (radioactive or fluorescent) VNTR probe, which binds only to the complementary repetitive sequences; the hybridised fragments are detected by autoradiography, producing a pattern of bands unique to each individual.

Final Answer:
DNA fingerprinting compares the unique VNTR band pattern of an individual's DNA (obtained via restriction digestion → electrophoresis → Southern blotting → probe hybridisation), and is widely used in forensic investigation and paternity testing.