In molecular biology a technique called a polymerase chain reaction is commonly used. Polymerase chain reaction is also abbreviated to PCR for ease of use. The name polymerase chain reaction is derived from the fact that a DNA polymerase is used to replicate or amplify itself by way of a chain reaction - thus the term polymerase chain reaction explains the process very accurately. The polymerase chain reaction can be as extensive or as limited as is desired - and the polymerase chain reaction is closely controlled to get the desired effect. The polymerase chain reaction almost always involves a form of heat stability, provided by a Taq polymerase, polymerase chain reaction methods also generally involve thermal cycling. This has the effect on the polymerase chain reaction of heating and cooling the PCR polymerase chain reaction on a continuous cycle, which helps separate the DNA strands in the polymerase chain reaction and make it possible to target specific DNA in the polymerase chain reaction to amplify.

A real time polymerase chain reaction (also called real time PCR) is a version of quantitative polymerase chain reaction in which, after every round of replication, the DNA is quantified. Real time polymerase chain reaction is often combined with reverse transcription polymerase chain reaction to particularly home in on a specific gene expression at a specific time, so this type of polymerase chain reaction allows a greater level of precision when needed.

Although the polymerase chain reaction has many different applications in research and diagnostic situations, real time polymerase chain reaction or real time PCR is most often used when looking to detect genes involved with infectious diseases and cancer. This type of polymerase chain reaction is also used with genetic conditions. The uses of polymerase chain reaction are many and varied.

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