Which was the first restriction endonuclease, whose functioning depended on a specific DNA nucleotide sequence, to be isolated and characterised?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Hind II
In 1963 two enzymes that restrict the growth of bacteriophage in Escherichia coli were isolated. One added methyl groups to DNA and the other cut DNA; the cutting enzyme was called a restriction endonuclease. Five years later the first restriction endonuclease that cut DNA at a specific nucleotide sequence was isolated and characterised. This was Hind II, which recognises a specific sequence of six base pairs. EcoR I, BamH I and Pst I are other restriction enzymes, whose sites are marked on the vector pBR322; none of them was the first.
NCERT Extract:
Restriction Enzymes – “In 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. 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.”