ABSTRACT
The nucleases of the gastrointestinal tract are rather broad in specificity and act on single-stranded Ribonucleic acid (RNA) or Deoxyribonucleic acid (DNA), while the restriction endonucleases are highly specific and act on double-stranded DNA only. DNA biochemically synthesized in the laboratory by DNA polymerase can be inserted in place of the foreign DNA to cause production of new proteins or of antisense RNA that inhibits the synthesis of one or more enzymes. Recombinant DNA technology is possible because of these highly specific types of enzymes. More than 600 restriction endonucleases are known, having first been discovered in 1968. The restriction endonucleases are used to specifically cut out a fragment of double-stranded DNA from a plasmid of a donor or host. More than 100 restriction endonucleases are supplied in pure form by biochemical companies. The polymerase chain reaction is routine in most recombinant DNA technology laboratories.
