Restriction endonuclease is also called restriction enzymes and works on the specific nucleotide sequence called restriction site. These enzymes restrict the entry of foreign DNA into bacteria.

Restriction enzyme recognizes specific restriction sites which are independent of DNA sources.

On the basis of properties restriction enzymes has been divided into type I, type II, and type III. Type I and Type III require ATP and magnesium while Type II requires only magnesium.

Isocaudomers recognizes different sequences but produces same ends while Isoschizomers recognizes the same sequences and cut in the same pattern.

DNA ligases are used to join DNA molecules together by synthesizing phosphodiester bond between the nucleotides.