What are restrictions enzyme. Mention their type with role in biotechnology.

Explanation

Restriction enzymes are enzymes that cleave DNA into fragments at or near specific recognition sites within the molecule. Restriction enzymes were isolated from E.coli in 1963. The restriction enzymes are classified into exonucleases and endonucleases based on their mode of action.
(i) Exonucleases are enzymes that remove nucleotides one at a time from the end of DNA molecule. Eg: Bal31, Exonuclease III.
(ii) Endonucleases are enzymes that break the internal phosphodiester bonds in DNA molecule. Eg: Hind II, EcoRI, Pvul, Bam HI, TagI.
Restriction endonucleases namely Type I, Type II, Type III, based on their mode of action. Inrecombinant DNA technology, the Type II enzyme is most preferred as they recognize and cut DNA within a specific sequence typically having 4-8bp.
The restriction enzyme Hind II always cut DNA molecules at a point of recognitionising a specific sequence of 6base pair, which is known as a recognition sequence. Today more that 900 restriction enzymes are available from 230 strains of bacteria.