PCR - (Jan/15/2004 )

i´m trying to amplify a 2kb and 548bp band from gDNA of mice but never got to see the big band. i don´t understand what happened! i´ve tried different conditions even to the point of putting 2 minutes for the extension but nothing happened.can anyone explain to me what had just occured?

thanks.

For me PCR is always a question of "magic".
I've tryed to set up the right conditions for many different amplifications. When the PCR is "good", it works in many different conditions.
But when I get no result, in my experience, changing parameters is just a waste of time.
The best thing to do is design a new set of primers and start form zero!