Restriction enzymes are used to remove from DNA a complete and undamaged structural gene coding region for the expression of DNA polymerase I (polA) without the gene's natural promoter or with only a significantly damaged portion of the gene's natural promoter. Also by the use of restriction enzymes,...http://www.google.es/patents/US4767708?utm_source=gb-gplus-sharePatente US4767708 - Enzyme amplification and purification
