Identify the correct sequence of steps involved in DNA fingerprinting.
(A) Separation of DNA fragments by electrophoresis
(B) Isolation of DNA
(C) Detection of hybridised DNA fragments by autoradiography
(D) Hybridisation using labelled VNTR probe
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B), (A), (D), (C)
(B) Isolation of DNA — comes first. The DNA must be taken out of the cells and purified before anything else can be done to it.
(A) Separation of DNA fragments by electrophoresis — comes second. The isolated DNA is first cut by restriction endonucleases, and the fragments are then sorted by size in a gel.
(D) Hybridisation using labelled VNTR probe — comes third. The separated fragments are blotted on to a nylon or nitrocellulose membrane. A radioactive VNTR probe is then added, and it pairs with the fragments that carry the matching repeats.
(C) Detection of hybridised DNA fragments by autoradiography — comes last. The radioactive probe darkens an X-ray film and shows the bands. This can be done only after the probe has bound.
Note: A similar question was also asked in CUET (UG) 2026 on 07-06-2026 (Slot 2) and on 20-05-2026 (Slot 2), in CUET (UG) 2025 on 23-05-2025 (Slot 2) and on 22-05-2025 (Slot 2), and in CUET (UG) 2023 on 23-06-2023 (Slot 3) and on 11-06-2023 (Slot 3).
NCERT Extract:
DNA Fingerprinting – …
