Some DNA amount added cannot achieve reproducible in AP-PCR?! (urgent!) - (Apr/11/2006 )

I used a range of amount of genomic DNA for AP-PCR (10ng, 15ng, 20ng and 30ng). I found that only 15ng DNA added can achieve reproducible. But other amount (10ng, 20ng and 30ng) cannot achieve reproducible. Does anybody know that why the results like that? I do not know the reason~~ HELP !! Thank !

what is your dna solubilized in? if it's in te then the edta contributed may be affecting the higher dna reactions. the lower dna reactions may just be too little dna.