Restriction Endonuclease Discovery — NEET Biology
✅ Asked in NEET 2026In the year 1963, the two enzymes responsible for restricting the growth of bacteriophage in Escherichia coli were isolated. One of these added methyl groups to DNA, while the other cut DNA. The later was called restriction endonuclease.
Restriction endonucleases are enzymes that cut DNA at specific recognition sites, discovered in 1963 while studying how E. coli protects itself from bacteriophages. NTA tests whether students understand that these enzymes are the 'scissors' of genetic engineering—paired with methylase enzymes that protect host DNA. Students often confuse restriction endonucleases with methylases (which add methyl groups) or forget that they cut DNA at specific sequences, not randomly. Remember: restriction endonucleases recognize and cut DNA at palindromic sequences, producing sticky or blunt ends. This discovery was revolutionary because it made recombinant DNA technology possible—the foundation of genetic engineering tested frequently in NEET.
Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular scissors. B. They restrict bacteriophage growth in E. coli. C. They cut DNA only at the centre of palindromic sites. D. They remove nucleotides only from ends of DNA fragments. E. They recognise specific palindromic base-pair sequences.
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