from Wittwer CT and Farrar JS (2011) in PCR Troubleshooting and Optimization

With 3 billion bases in the human genome, it is not easy to find and analyze the small sequence regions that confirm a genetic disorder, identify an oncogenic change or detect microbial infection. The polymerase chain reaction (PCR) provides this focus. Since its development 25 years ago, it has become the most important tool for working with nucleic acids in molecular biology and clinical diagnostics. It deserves such central recognition because of its simplicity.

Before PCR, molecular methods were multi-stepped, laborious and time consuming. To amplify DNA, it had to be cloned into plasmids, the plasmids inserted into bacteria, the bacteria grown in culture, the bacteria harvested, the plasmids isolated from the bacteria, and the DNA inserts separated from the plasmid DNA. Southern blotting required multiple steps of restriction enzyme digestion, electrophoresis, blotting onto membranes, hybridization with radioactively-labeled oligonucleotide probes and development on X-ray film. These early techniques required large amounts of DNA and strong technical expertise for consistent results.

PCR greatly reduced the number of steps required to generate appreciable quantities of DNA necessary for many applications. The acceptance of PCR in the scientific community was relatively swift, with an independent research group using the technique within a year. PCR has revolutionized molecular biology and clinical diagnostics. (Wittwer and Farrar, 2011 in PCR Troubleshooting and Optimization)

PCR is simple and elegant. It is remarkably robust and tolerates the addition of many diverse reagents such as electrophoresis dyes (Wittwer and Farrar, 2011 in PCR Troubleshooting and Optimization).