The first restriction endonuclease to be isolated, whose functioning depends on a specific DNA nucleotide sequence, always cuts DNA molecules at a particular point by recognising a specific sequence of six base pairs. Identify this enzyme.

Step-by-step solution

The first restriction endonuclease to be isolated was Hind II. Its functioning depends on a specific DNA nucleotide sequence. It was found that Hind II always cuts DNA molecules at a particular point by recognising a specific sequence of six base pairs, which is known as its recognition sequence. EcoRI, Hind III, and BamHI are also restriction endonucleases but they were not the first to be isolated. Therefore, the correct enzyme is Hind II. Answer: Hind II