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pcr contamination - (Feb/26/2006 )

hi all
im new to molecular biol techniques
im desp owing to pcr contamination
not sure if its contamination
my problem is that im getting bands in negative controls
and their size is exactly same as expected dna size
but puzzling thing is my water shows no band
so i really doubt if its contamination
i do pre and post pcr reactions and prepare master mix in separate areas


what is pcr template and -ve control u r telling water didnt show any band then -ve control is water or other? or intensity of the same bands are same? and if no, u r templates are different and u r primer also binds weakly and giving the +ve result and keep tm according to that primer 2nd thing is loading in a gel perfectly without spill into other well and tell me -ve control if u not got any improvemt by looking at this ok


Karol, would you please tell us what is in your neg control and what is in your water control? the difference between the two might find the source of the contamination...

also, what is the size of the band? is it a small band? I am wondering about the potential for primer-dimer


primer dimers appears as a smear at 200bp roughly. If your product is in this range you may have an artefact as aimikins showed up...