PCR artifacts

[rcha244 at bay.cc.kcl.ac.uk]

I am having some unusual pcr artifacts with a batch of taq from a new 
supplier. I consistently get a ladder effect up to the major band which 
is of expected size. I have tried various titrations of DNA, Mg, primers 
and Taq which dont eliminate the problem entirely. The pcr is a 
reampification of them same fragment. I have also seen it with RTPCR 
products. Any suggestions?

Paul Crossey 
Dept of Medicine
KCSMD
London