Polimerase Chain Reaction (PCR)

Polymerase Chain Reaction, or PCR, is a process which permits scientists to make unlimited copies of genes. This is done with a single molecule of DNA. One hundred billion copies of the DNA can be generated in a few hours.

This technique is currently being used to investigate Andy's CMV because of a positive CMV antigen on his blood.

More definitions of PCR on the web via Google here.

More via Wikipedia here.