Patent ID: 7220544

Claim:
A method for detecting a target nucleic acid having a target sequence in a sample, comprising the steps of: (a) obtaining a first probe comprising a nucleic acid which has a specific region having a sequence complementary to the target sequence and a nonspecific region having a sequence that is not complementary to the target sequence of the target nucleic acid; and a second probe comprising a nucleic acid which has a first region that is complementary to at least a portion of the nonspecific region of the first probe, a loop region that does not have a sequence complementary to the first probe, and a second region that is complementary to at least a portion of the specific region of the first probe, wherein the nucleic acid of the second probe is labeled with a labeling material generating a signal by which formation of a loop can be detected; (b) mixing the first probe and the second probe, thereby forming a mixture wherein the loop in the loop region of the second probe is formed when the second probe is annealed with first probe, thereby quenching the signal from the labeling material in the absence of a target nucleic acid; (c) adding the sample to the mixture of step (b), whereby the target nucleic acid in the sample anneals with the first probe, thereby releasing the second probe; and (d) detecting an increase in the signal of the labeling material in the presence of the target nucleic acid compared to the signal obtained in step (b), thereby detecting the target nucleic acid, wherein the signal is quenched when the first probe and the second probe are annealed and not quenched when the first probe and the second probe are not annealed.