Figure 13.

The real-time PCR; in this system, a specific probe labelled to two types of fluorophores, referred to as R for reporter (donor) and Q for quencher (or receptor), sits in the interval of two primers. When the distance between two fluorophores is between 1 and 10 nm, any the excited energy of the R is donated to Q in the form of Fluorescence Resonance Energy Transfer (FRET). Through amplification of the DNA, the R is cut by the amplifier enzyme, which lead to the separation of R and D fluorophores and emission of fluorescence. The level of emission is linearly proportional to the number of probe and genome.