Best way to store DNA?

Hiranya Roychowdhury hroychow at NMSU.EDU
Wed Jul 15 09:58:17 EST 1998

At 12:49 PM 7/14/98 -0700, John Ladasky wrote:
>In article <6ogb83$qde at>,
>Conrad R Fjetland <fjetland at> wrote:
>>Granger L. Ridout (granger.ridout at wrote:
>>: Please forgive this possibly dumb question, but what is the best way to
>>: store ... DNA after EtOH precipitation?  ...
>>: G.L.Ridout

>	Most DNA samples still contain residual nuclease activity, even af-
>ter purification.  It is probably wisest to store them at 4 degrees rather
>than at room temperature.
>Rainforest laid low.
>"Wake up and smell the ozone,"
>Says man with chainsaw.					- John Ladasky

DNase, if present in the sample, will degrade DNA, albeit slowly, even at 4
C. In fact, I had done a test, following a similar comment by one of our
grad students. I added some DNaseI to three equal aliquotes of a plasmid
prep that I knew was quite free of any. One of the aliquotes I incubated on
the bench, the second was incubated at 4 C (cold rm) and the third was
stored at -20. The plasmid in the tube at RT was all but gone after an hour.
The tube stored at 4 C had all its DNA degraded after 5h and the tube at -20
showed the presence of plasmid for about a week (with smearing below the
band), the final gel showing no trace of any plasmid. In the case of the -20
tube, it is hard to infer if the DNaseI was active at that temp. The
degradation could have been during the daily thawing of the sample for the
        No, I did not do this in triplicates.   

Dr. Hiranya Sankar Roychowdhury
Plant Genetic Engineering Lab.
New Mexico State University
Las Cruces, NM 88003
Ph. (505) 646-5785
hroychow at

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