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What's the highest DNA concentration for PCR? - before being inhibited? (Nov/23/2010 )

The title says it all. Does anyone knows the range of DNA concentration where you'd start getting smears and/or inhibition? Is it in the ng or ug range?
Thank you and Happy Thanksgiving.
M.

-Maddie-

Depends on the type of DNA. Roche Lab FAQs says it is 500 ng for human genomic, 10 ng for bacterial genomic and 500 for plasmid.

-bob1-

and it depends also on how specific your primers are and how stringent are the PCR conditions.

-perneseblue-

over 1 ug of both DNA and RNA gives me smear always.

-Curtis-

why is it different between human and bacteria?

-Maddie-

bacterial genome is much smaller, so 10 ng has more copies of each gene is my guess.

-bob1-

You can easily do cycle titration to test for your own sample. You can remove some DNA sample every 5 cycle during PCR and run on the gel. Good luck.
http://www.bioprotocols.info/index.php

-chromatin-

bob1 on Wed Nov 24 22:29:11 2010 said:


bacterial genome is much smaller, so 10 ng has more copies of each gene is my guess.

I though the inhibition was caused by a tube "too crowded" where the primers and enzymes can't find their target.

-Maddie-