Restriction Enzymes & Recognition Sequences — NEET Biology
✅ Asked in NEET 2024The 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.
Restriction endonucleases (like Hind II) recognize and cut DNA at specific base pair sequences called recognition sequences, typically 6 bp long. Over 900 such enzymes exist in different bacterial strains, each cutting at different recognition sites. Students commonly confuse whether restriction enzymes recognize the same sequence across all enzymes (wrong) versus each enzyme having its own unique recognition sequence (correct). Remember: each restriction enzyme is specific to its own recognition sequence—Hind II cuts at its site, Eco RI at its site, and so on. This specificity is fundamental to molecular cloning and is repeatedly tested because it's the basis for DNA fingerprinting and recombinant DNA technology.
This paragraph was tested 4 times in NEET.
Statement I: Restriction Endonuclease finds its specific recognition sequence and binds to the DNA. Statement II: Restriction Endonuclease cuts each of the two strands of the double helix at specific points in their sugar phosphate backbones. Choose the correct answer: (NEET 2024)
Hind II always cuts DNA molecules at a particular point called recognition sequence and it consists of: (NEET 2024)
Identify the wrong statement with regard to restriction enzymes. (NEET 2020)
Which of the following is a restriction endonuclease? (NEET 2016 Phase 1)
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