The polymerase chain reaction (PCR) is a biochemistry and molecular biology technique for isolating and exponentially amplifying a fragment of DNA, via enzymatic replication, without using a living organism.
It enables the detection of specific strands of DNA by making millions of copies of a target genetic sequence.
The target sequence is essentially photocopied at an exponential rate, and simple visualisation techniques can make the millions of copies easy to see.
The method works by pairing the targeted genetic sequence with custom designed complementary bits of DNA called primers.
Irrespective of the variety of methods used for DNA analysis, only PCR in its different formats has been widely applied in GMO detection/analysis and generally accepted for regulatory compliance purposes.
QRT-PCR methods use fluorescent dyes, such as Sybr Green, or fluorophore-containing DNA probes, such as TaqMan, to measure the amount of amplified product in real time.
Annealing temperatures for each of the primer sets must be optimized to work correctly within a single reaction, and amplicon sizes, i.e., their base pair length, should be different enough to form distinct bands when visualized by gel electrophoresis.
This approach is ideal to precisely identify a GMO, yet highly similar GMOs will pass completely unnoticed.
Some combined testing methods could give results that would triple the actual GM content of a sample containing this GMO.
After genetic elements characteristic of GMOs are selected, methods and tools are developed for detecting them in test samples.
Near infrared fluorescence (NIR) detection is a method that can reveal what kinds of chemicals are present in a sample based on their physical properties.
Although the technique would require advanced machinery and data processing tools, a non-chemical approach could have some advantages such as lower costs and enhanced speed and mobility.