Single nucleotide detection method

A multi-component biological probe system, comprising (a) a first single-stranded oligonucleotide labelled with one or more fluorophores in an undetectable state and one or more quenchers, and (b) second and third unlabelled single-stranded oligonucleotides capable of hybridising respectively to complementary 3′ side and 5′ side flanking regions on the first oligonucleotide which are juxtaposed either side of a single nucleotide capture region,

• wherein the 5′ end of the second oligonucleotide and the 3′ end of the third oligonucleotide are connected by a linker region, and
• wherein the third oligonucleotide includes an element resistant to exonucleolytic degradation at its 3′ end.