The overlap extension polymerase chain reaction (or OE-PCR) is a variant of PCR. It is also referred to as Splicing by overlap extension / Splicing by overhang extension (SOE) PCR. It is used assemble multiple smaller double stranded DNA fragments into a larger DNA sequence. OE-PCR is widely used to insert mutations at specific points in a sequence or to assemble custom DNA sequence from smaller DNA fragments into a larger polynucleotide.