Molecular beacon | definition of molecular beacon by Medical dictionary
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molecular beacon a dual labelled OLIGONUCLEOTIDE PROBE, with a fluorescent reporter group at one end and a fluorescence quencher group at the other, that reports the presence of target nucleic acid molecules in solution by fluorescing. In the absence of a HYBRIDIZATION target, the probe forms an internal HAIRPIN structure that brings the reporter and quencher groups into close proximity, resulting in the quenching of fluorescence. In the presence of a hybridization target, the probe molecule unfolds and hybridizes to the target. Reporter and quencher are now physically separated and the reporter dye can fluoresce on stimulation, indicative of hybrid formation. Such a probe is useful in situations where it is not possible or desirable to isolate probe-target hybrids from an excess of the probe.