How many reverse and forward primer copies need to be added to the PCR mix?

I know that you need 2 primers for any type of PCR: a forward and a reverse primer. However, how many copies of those forward and reverse primers do you have to add? Since the template gets copied exponentially, how do you not run out of enough primers to copy all of the strands? Or do the primers detach... show more I know that you need 2 primers for any type of PCR: a forward and a reverse primer. However, how many copies of those forward and reverse primers do you have to add? Since the template gets copied exponentially, how do you not run out of enough primers to copy all of the strands?

Or do the primers detach themselves so that they can be used again? This would not make sense since you sometimes have your target site as part of the primer or you add a restriction site to the 5' end of the primer and you wouldn't want those to be detached.

Thanks.
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