Inverse PCR is used to amplify and clone unknown DNA that flanks one end of a known DNA sequence and for which no primers are available.  The technique involves digestion by a restriction enzyme of a preparation of DNA containing the known sequence and its flanking region.  The individual restriction fragments (many thousands in the case of total mammalian genomic DNA) are converted into circles by intramolecular ligation, and the circularized DNA is then used as a template in the PCR.

Protocol: Inverse PCR Protocol II