Quantity of PCR Products

stewartl at best.com stewartl at best.com
Wed Sep 30 05:25:40 EST 1998

In article <01bdec0c$bbd1e660$d0dcd8d1 at localhost.adnc.com>,
  "rhmorse" <rhmorse at genbiosys.com> wrote:
> I am trying to get some "ball-park" quantities of the amount of DNA
> typically generated as a result of amplification by PCR.  I realize this
> depends upon the amount of starting DNA and the efficiency of the PCR
> reaction.  But, by an order of magnitude, what is the amount of DNA you end
> up with?

Optimum yield for a given number of cycles can be approximated using the

                  2^n x initial number of copies. n = # of cycles 

There is an exponential phase of amplification in PCR until the number
of product copies reaches approximately 1012. After this point the
accumulation of product amplification generally drops off dramatically
and the product stops accumulating exponentially. The number of cycles
needed to reach this point can be approximated with the formula: 

                  Nf = No(1 + Y)^n 

                  Where Nf is the final number of the double stranded
target sequence 
                  No is the original number of target copies 
                  Y is the efficiency per cycle of the polymerase 
                  n is the number of cycles 

You can find more information about what affects the efficiency,
fidelity, and specificity of a PCR reaction at

Good luck.


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