Extracting DNA from fixed tissue?

dkim at unm.edu dkim at unm.edu
Fri May 27 10:19:28 EST 1994

Question was posted about DNA extraction for fixed tissue.

If your intention is to use this DNA for the PCR, you may want to forgo any
further manipulation after the overnight proteinase K step.

The proteinase K should have auto-inactivated after such a long incubation
(we use overnight at 37 C or 3 hours at 60 C.). After this, the DNA should
be amplifiable without further purification.

I don't know if formaldehyde is an inhibitor of the enzyme. Our procedure for
embedded tissue is to dissoolve wax away in Xylene, then wash in ethanol, air
dry, then add proteinase K mix. The dehydrated tissue crumbles away (spleen 
sections) into a powder in the digestion mix. Spin out the tissue and use a 
small portion of the supernatant as template.

A possible problem may occur due to too much lipid in brain tissue, so a
 xylene extraction may not be a bad idea for you.

Daniel Kim  kim at flovax.lanl.gov

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