Endonucleases
A class of nuclease which hydrolyses the middle of the polynucleotide chain of a nucleic acid[1], by cleavage of the phosphodiester bond. Endonucleases can be non-specific (cleaving indiscriminately along the polynucleotide) or they can be specific, cutting at certain sites which are recognised by the enzyme; these are called restriction endonucleases.[2]