PCR: Why is my TAQ unfaithful

[Julie Wilberding]

Hi,

I have been tying to PCR three constructs.  I use Promega TAQ, 100uM
dNTP's, buffer and the proper amount of primers and template (Double
stranded circular plasmid).  My mutation rate is high ( 3 in one 180 bp
fragment).  I have changed dNTP, TAQ, with no change.  This is a problem
recently encountered in our lab.  The PCR conditions are 94 1 min., 55 1
min., 72 2 min., 30 cycles with a final cycle b3ing a 10 min extension at
72.  Is the circular template a possible cause???  Efficiency is good but
fidelity sucks!  Any help or advice would be greatly appreciated.

Julie