Patent ID: 7919252

Claim:
A method of detecting a target sequence portion of a nucleic acid comprising: providing for measurement a stem-and-loop structured nucleic acid, which comprises a double-stranded portion being formed by hybridization of complementary sequence portions on a nucleic acid strand; and a looped single-stranded portion containing a target sequence portion which connects the two complementary sequence portions; providing an immobilized probe nucleic acid having a sequence complementary to the target sequence portion which is immobilized at one end to a solid substrate surface; reacting the stem-and-looped nucleic acid provided for measurement with the immobilized probe nucleic acid for a time and under conditions sufficient to specifically hybridize the target sequence portion of the stem-and-loop nucleic acid provided for measurement to the immobilized probe nucleic acid; and detecting presence or absence of hybridization between the stem-and-loop structured nucleic acid provided for measurement and the immobilized probe nucleic acid, and detecting the target nucleic acid sequence when hybridization occurs; wherein 5′ to 3′ sequence orientations of both the immobilized probe nucleic acid and the target sequence portion are arranged so that the double-stranded portion of the nucleic acid for measurement extends away from the solid surface when the probe nucleic acid and the target sequence portion are hybridized.