The use of alkaline phosphatase to prevent vector regeneration

Linearized plasmid vector molecules produced by restriction enzyme digestion can be reformed into circles by the action of DNA ligase. This is the most favorable reaction even when foreign DNA fragments are present. Thus, unless a direct selection technique is available, the reformed parental molecule will also give transformants and hence reduce the overall cloning efficiency. Usually most of the recircularized parental plasmids can readily be distinguished from recombinants by the absence of insertional inactivation; nevertheless, this may involve screening large numbers of transformants for each recombinant.