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Who can tell me the difference of these two terms? - Help me (Nov/09/2005 )

Hi Everyone!

I am a novice on molecular biology.
Who can tel me in detail the difference between the Touch down PCR and gradient PCR , and each application ? Thanks for your patient answer!


gradient pcr is doen by a machine that is capable of having a different temperature in each row of wells. That way you can pcr using a range of annealing temps all at the same time, but a single sample goes through all of the pcr cycles at the same annealing temp.

touchdown pcr is done by changing the annealing temperature of the same sample in different cycles usually you start high and then decrease the annealing temperature in subsequent cycles.


here are two relevant links : and for touchdown PCR for gradient PCR

application of gradient pcr (just on of the many examples...) (smilar to


Much Thanks for Beccaf22 and Fred33's patient and detailed wnswer!