Question

What is DNA fingerprinting technique? Describe in detail with a diagram.

Hint:

VNTR variation + restriction digestion + gel electrophoresis + Southern blotting + probe hybridization = unique band pattern.

Answer 1

Step 1: Define DNA fingerprinting (2 marks):
DNA fingerprinting is a technique that identifies differences in specific regions of DNA sequences (called VNTRs - Variable Number of Tandem Repeats, which vary greatly between individuals) to create a unique identifying pattern for each person, used in forensics, paternity testing, and identification; it was developed by Alec Jeffreys.

Step 2: Describe the procedure step by step (3 marks):
The main steps are: (1) DNA isolation from a sample (blood, hair root, etc.); (2) digestion of the DNA using restriction endonuclease enzymes into fragments; (3) separation of fragments by size using gel electrophoresis; (4) transfer of the separated DNA onto a synthetic membrane (nylon/nitrocellulose) by Southern blotting; (5) hybridization of the membrane with a labelled (radioactive or fluorescent) VNTR probe; (6) detection of the hybridized fragments by autoradiography, producing a pattern of bands unique to that individual (like a barcode).

Final Answer:
DNA fingerprinting uses VNTR sequence variation, revealed through restriction digestion, gel electrophoresis, Southern blotting and probe hybridization, to generate a unique band pattern identifying an individual (a diagram would show this sequence: DNA to restriction fragments to gel-separated bands to blotted membrane to hybridized/detected pattern).