PCR – Polymerase Chain Reaction

Kary Mullis – PCR Testing was first discovered by Kary Mullis in 1983 and is now widely used as diversely as diagnostics, forensics, genetic testing and cloning.

The PCR process is for amplifying DNA in a sample to detectable levels. This is very useful for small sample sizes. Some organisms such as viruses will contain only RNA and because of this, a reverse transcription process will convert the RNA to complimentary DNA (cDNA), which is used for the test. The earliest PCR processes were labour intensive and took many hours. Modern equipment will automate the process and diagnostic test results can be available in less than 2 hours.

All parts of the PCR test are carried out automatically within the analyser. 

To amplify a segment of DNA using PCR, the sample is first heated so the DNA denatures, or separates into two pieces of single-stranded DNA. Next, an enzyme called "Taq polymerase" synthesizes - builds - two new strands of DNA, using the original strands as templates. This process results in the duplication of the original DNA, with each of the new molecules containing one old and one new strand of DNA. Then each of these strands can be used to create two new copies, and so on, and so on. The cycle of denaturing and synthesizing new DNA is repeated as many as 30 or 40 times, leading to more than one billion exact copies of the original DNA segment.