EcoRI, a significant tool in rDNA technology is -

The correct answer is Option (3) → Enzyme

EcoRI is a restriction endonuclease, often called the “molecular scissors” of recombinant DNA technology. It cuts DNA at the palindrome GAATTC and leaves sticky ends. Its name tells where it came from: E for the genus Escherichia, co for coli, R for the strain RY13, and I because it was the first enzyme taken from that strain.

Option (1) Bacteria — Incorrect. EcoRI is isolated from a bacterium, E. coli. It is not the bacterium itself.

Option (2) Plasmid — Incorrect. A plasmid is a small circular DNA used as a vector, such as pBR322. EcoRI is used to cut it open.

Option (3) Enzyme — Correct. Restriction endonucleases are enzymes of the nuclease class that cut DNA at specific points.

Option (4) Purine — Incorrect. A purine is a nitrogenous base (adenine or guanine), a part of DNA, not a tool that acts on it.

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. This specific base sequence is known as the recognition sequence for Hind II. Besides Hind II, today we know more than 900 restriction enzymes that have been isolated from over 230 strains of bacteria each of which recognise different recognition sequences. The convention for naming these enzymes is the first letter of the name comes from the genus and the second two letters come from the species of the prokaryotic cell from which they were isolated, e.g., EcoRI comes from Escherichia coli RY 13. In EcoRI, the letter ‘R’ is derived from the name of strain. Roman numbers following the names indicate the order in which the enzymes were isolated from that strain of bacteria.”