Restriction enzymes

 Restriction Enzymes, or Restriction Endonucleases cut DNA into smaller fragments (Alberts et al., 2008).

There are two kinds of restriction enzymes, there is Endonuclease and Exonuclease. Exonuclease digests ends of DNA whereas Endonuclease digests in-between the ends.

Different restriction enzymes recognise different squences, normally between 4 to 8 nucleotides in length. Some restriction enzymes produce staggered or 'sticky' ends while others leave blunt ends (Alberts et al., 2008). Examples of restriction enzymes that produce staggered ends are EcoR1 and Hind111 (Dryden et al., 2013). Hpal is an example of a restriction enzyme that forms blunt ends (Alberts et al., 2008). 

Restriction Enzymes are often used to create recombinant DNA molecules. See Recombinant_DNA_Technology.

References

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P., 2008. Molecular Biology of the Cell. 5th Ed. New York: Garland Science

Dryden, D.T.F., Loenen, W.A.M., Murray, N.E., Raleigh, E.A., Wilson, G.G., 2013. Highlights of the DNA Cutters: a short history of restriction enzymes. Nucleic Acids Research, 42(1), pp 3-19.