PCR specificity

[Els Van Geldre]

Hi there,

Lately, I performed some PCR reactions with different MgCl2 
concentrations (1.5mM, 3mM and 4.5 mM) in order to optimize my PCR 
conditions. What surprised me was that with the same primercombination 
and template, but different MgCl2 concentration, I got products of 
diffent lengths. In other cases the MgCl2 concentration influenced the 
number of PCR products I obtained (from 1 PCR product to 5 PCR products 
for the same primercombination and template, but other MgCl2 
concentration). I am aware of the fact that MgCl2 plays a very important 
role in PCR succes, but is it normal that it also influences the number 
of PCR products and thus the specificity of the PCR reaction ?

Thanks for answering,
Els