Smear after PCR - No band but smear were found from my samples (Jan/24/2006 )

Anyone can help me with my PCR problem?

I was trying to test the food matrix effect of my PCR assay, but to my surprise all the wells with food sample and bacteria showed no bands at all. There were only smears.

What could have been the cause to smear formation?

Js

a smear often means you have added too much DNA into your PCR. The way I understand it, too much DNA in a PCR reaction will result in all the primers being 'soaked' up by binding non-specifically to the DNA. As a result, you get products off different sizes resulting in a smear when you run the gel Try diluting your samples 1:100. I have diluted DNA up to 1:10,000 and successfully gotten a product.

Thx...
I will give it a try

But how should I do the dilution?
Do I dilute the sample before cell lysis or after cell lysis?

Are you lysing cells and then using the lysate? Or are you etracting DNa and cleaning it up? Either way, just dilute the template you are adding to your sample. SO dilute the lysate using either pure dH2o or 1:10 TE buffer.