Patent ID: 8772464

Claim:
A nucleic acid comprising: (i) an aptamer comprising a 5′-end switching aptamer stem sequence; and (ii) a 3′-end priming sequence; wherein: (1) in a first conformation, the 3′-end priming sequence forms a hairpin structure, and the 5′-end switching aptamer stem sequence is single-stranded; and, (2) in a second conformation, the 5′-end switching aptamer stem sequence hybridizes to a complementary region of the nucleic acid, and the 3′-end priming sequence is available for hybridization to a target template to form a primer:template pair; wherein binding to a ligand by the aptamer induces a conformational change of the nucleic acid to shift between the first conformation and the second conformation, or between the second conformation and the first conformation.