Smeared PCR products

Cheryl C Jerome cjerome at uoguelph.ca
Tue Feb 21 14:31:16 EST 1995


Hello.  I am wondering if anyone can help me.  I have been having PCR 
problems for a couple of months. I have been having consistent smearing 
with my PCR amplified product.  A bright smear starts at my PCR product 
and extends to my primers.  Since my PCR product is large (2.8 KB) it is 
a very large smear which extends to my PCR band.  The smearing is also in 
the negative control. I have replaced my Taq, my primers, dNTPs, etc... 
to try to figure out what the problem is.  Also, I am running a positive 
control with DNA which has worked well in the past.  I had the PCR 
working with the same conditions and primers for about 2 months.  Then, I 
was sequencing for about a month and was not running PCR --- when I 
started to run PCR again, I had the smears and have not been able to 
resolve the problem.  I have reautoclaved water, etc...  Is it possible 
there is something in my water source?  What causes smearing?  I would 
appreciate any suggestions. Thank you. Cheryl



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