====================================== Touchdown PCR ====================================== This protocol describes one `method `_ to PCR a difficult product. The idea is to start at a high annealing temperature (Ta) and "touchdown" so you start at the most specific product and amplify at progressively less specific Ta's. Touchdown PCR --------------------------------- =============================== =========================== Cycle # Ta =============================== =========================== 1 72°C 2 71°C 3 70°C 4 69°C ... ... n Predicted Ta Repeat last cycle (30-n) times Predicted Ta =============================== =========================== .. note:: You could go even lower than the predicted Ta (we've gone down to 57°C as a robust protocol)