How much PCR template?

[Nick Jacobsen]

Hi there,
        Ive often asked myself the same questions. When PCRing 200bp 
from a cosmid Ive found that less template gives rise to a better 
amplimer yield. You could speculate that if you swamp the reaction 
with template PCR priming will occur preferentially with the initial 
template. You want this to occur in the initial stages but not in 
later stages when you want exponential amplification. The initial 
template maybe too complex to provide efficient amplification later 
on. I find that for genomic clones 1ng DNA is sufficient and for 
genomic DNA approx. 30ng (in 12ul) works fine.


cheers 

Nick.