A kind of polymerase chain reaction that is used for the amplification of DNA with a single known sequence is known as an inverse polymerase chain reaction (PCR).
It's a technique that allows PCR just when one internal sequence is known or recognized.
This is very useful for matching flanking sequences to various genomic inserts.
Before, being cut by an endonuclease, a sequence of self-ligation and digestion is performed. This leads to known sequences at both ends of the unknown sequences.