A fluorescence detection system consists of a detection probe with a reporter dye at the 5′ end (the tail), followed by a structure containing the complementary probe sequence (the stem) and the loop, quencher dye and a PCR primer at the 3′ end (the primer). Between the primer and its tail (the probe), a blocking agent (DNA spacer/PCR stopper, hexaethylene glycol ‘HEG’) is placed. This structure makes the sequence-specific priming and probing a unimolecular event that creates enough specificity for allelic discrimination assays. When not annealed to the target (downstream of the primer) the reporter dye fluorescence is quenched, when the extension occurs, the probe end of the scorpion binds to the target and the reporter and quencher separate resulting in fluorescence emission. Scorpion primer and probe hybridize to the same strand and thus the detection is faster than those achieved by hybridization or hydrolysis probes (Didenko, 2001). The scorpion chemistry can be used for genotyping (with or without ARMS principle) or qPCR. See How it Works and Scorpion Technology.