PCR problem - please help

Vince Mulholland mulholl at sasa.gov.uk
Fri Jun 23 06:57:48 EST 1995


I've got a contaminating band in my PCR reactions. I'm using 
allele-specific amplification to differentiate between species of 
nematodes. The set-up is as follows;

       'A'-specific         'B'-specific                    Universal
            -->                  -->                          <--
          390 bp               240 bp

So, the PCR reaction contains three primers. I get a particular band 
for each species or both bands when there is a mixture. This has been 
working fine up until a few weeks ago. I still get a single band when 
I amplify a single species. However, when there is a mixture of the 
two species I get a contaminating 800 bp band. This is the odd part - 
it is ONLY present when there is a mixture.

Anyone had similar problems? Any ideas gratefully accepted.


Thanks in advance,




Vincent Mulholland

Higher Scientific Officer,
Diagnostics & Molecular Biology Section,
Scottish Agricultural Science Agency,
East Craigs,
Edinburgh EH12 8NJ,
U.K.

E-Mail:	mulholl at sasa.gov.uk
Tel: 	(0131) 244 8845
Fax: 	(0131) 244 8912






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