Polymerase Chin Reaction is a technique that takes specific sequences of DNA of small and amplifies it to be used for further testing. it is also said to be as the Invitro Technique.We have seen an photocopy machine in an office, by which we can copy several pages. So, is the PCR machine in a molecular biology laboratory. PCR is DNA raplication ina test tube. Dr Kary Mullis developed PCR. To amplify lot of double stranded DNA molecules with same size and sequence by enzymatic method and cycling condition.