SMEAR IN POSITIVE CONTROL IN LONG PCR - (Jun/04/2006 )

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HI friends
from last 1 month i am trying to amplify a 2.8 kb gene from mustard by xt5 polymerase but sometime its give band with light smear and sometime complete smear from wells is there. i have tryied all conc of template & mgcl2. i am also getting smear in positive control ie without template , i have changed all component still i am getting smear . what may b the reason for this plz help me

Hi freind,
Since you also getting smear in the reaction without template, I think it is something to do with your primer or sub-optimum PCR condition.

Could you please provide us the following information:
-MgCl2 concentration
-dNTP concentration
-Primer concentration, GC% and Tm
-Taq unit that you use.
-Annealing Temp and Extension Time

and finally, please attached you gel photo.

Thanks