Which was the first restriction endonuclease discovered?

The correct answer is Option (3) → Hind II

Option (1) EcoRI — Incorrect. EcoRI comes from E. coli RY 13 and cuts at GAATTC. It is widely used, but it was not the first to be found.

Option (2) BamH I — Incorrect. BamH I is another restriction enzyme, used for example to insert genes into the tetracycline resistance gene of pBR322.

Option (3) Hind II — Correct. The first restriction endonuclease discovered was Hind II. Its function depended on a specific DNA sequence: it always cut DNA at a particular point by recognising a sequence of six base pairs.

Option (4) Pst I — Incorrect. Pst I is a restriction site in pBR322; it is not the first enzyme discovered.

Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 1), on 21-05-2026 (Slot 1), on 19-05-2026 (Slot 2) and on 14-05-2026 (Slot 1), in CUET (UG) 2025 on 13-05-2025 (Slot 1), in CUET (UG) 2023 on 09-06-2023 (Slot 3) and on 01-06-2023 (Slot 3), and in CUET (UG) 2022 on 20-08-2022 (Slot 1).

NCERT Extract:
Restriction Enzymes – “… The first restriction endonuclease–Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterised five years later. It was found that Hind II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs.”