PCR is Polymerase Chain Reaction.

It is used for making multiple copies of the gene. Hence PCR is used for

$\bullet$ The amplification of gene fragments (Gene amplification).

$\bullet$ PCR-based assays have been developed that detect the presence of gene sequences of the infectious agents.

$\bullet$ Proof-reading PCR (PR-PCR) is designed to detect known mutations within genomic DNA.

$\bullet$ Protein is not the target of PCR. Hence, plays no role in its purification.