How many restriction enzymes have been isolated from over 230 strains
of bacteria ?
Answer & explanation
Correct answer: option 1
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.