Commonly used dual-labeled probes

3' modification	5' modification
TAMRA	6-FAM, HEX, TET
Dabcyl	Fluorescein, 6-FAM, HEX, TET, Cy5, Cy3, TAMRA, ROX, Texas Red, Oregon Green
BHQ	Fluorescein, 6-FAM, HEX, TET, Cy5, Cy3, TAMRA, ROX, Texas Red, Oregon Green

Standard dual-labeled probes typically contain TAMRA at the 3' end and 6-FAM, HEX, or TET as a 5' reporter dye. These probes are commonly used with quantitative, real-time thermal cyclers, such as ABI. Sequence Detection Systems (ABI GeneAmp 5700 and ABI PRISM 7700 and 7900HT) and the LightCycler System. During the extension phase of the PCR, the 5' – 3' exonuclease activity of Taq DNA polymerase cleaves the fluorophore from the quencher. This results in detectable fluorescence that is directly proportional to the amount of accumulated target.