Method for detecting target nucleic acid and nucleic acid probe used therein

A second nucleic acid probe for detecting a target nucleic acid,

• wherein the target nucleic acid comprises a probe-binding region with which the second nucleic acid probe hybridizes;
• at least one terminal of the probe-binding region is a guanine base, and one or more single nucleotide polymorphisms are present within 1 to 7 bases from the guanine base in the probe-binding region;
• the second nucleic acid probe comprises an oligonucleotide having a cytosine base facing the guanine base on a terminal and a fluorescent dye conjugated to the cytosine base;
• the fluorescent dye is a fluorescent dye that is quenched by the interaction with a guanine base;
• the oligonucleotide is complementary to the nucleic acid in the probe-binding region except the one or more single nucleotide polymorphisms within 1 to 7 bases from the terminal guanine base;
• one or more bases in the oligonucleotide facing the one or more single nucleotide polymorphisms are a guanine base or a base having no fluorescence-quenching effect;
• provided that the base in the oligonucleotide facing the single nucleotide polymorphism closest to the terminal guanine base among the one or more single nucleotide polymorphisms is a base having no fluorescence-quenching effect.