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)