(a) Schematic for implementing a synthetic “telomerase” with a single PER hairpin. (b) A PAGE denaturing gel showing telomerization under different hairpin concentrations. 100 nM primers were incubated with the hairpins for 4 hours at 37 °C with dATP, dTTP, and dCTP at 100 μM. (c) Schematic for signal amplifier, where a miRNA target activates the synthesis of fluorescent telomere strands. (d) System components and reaction diagram for the signal amplifier. A gated hairpin (A) and telomerase hairpin (B) are designed to react to the detection of a miRNA signal and concatenate repeats of the human telomeric sequence TTAGGG, into which Thioflavin (ThT) intercalates. (e) A native PAGE gel showing conditional telomerization in the presence of 10 nM miRNA signal for 4 hours at 37 °C with dATP, dTTP, and dGTP at 100 μM. Primer P and hairpins A and B were held at 100 nM, 10 nM, and 1 μM, respectively. The protector for hairpin A was at 15 nM. Target detection can be visualized with a blue light transilluminator through the amber filter unit (vis) and on a Typhoon scanner (FAM). See Methods section for additional details.