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For direct use as template in PCR runs. Chelex 100 5-10% w/v extraction. Without listing the whole protocol, in the end the supernate is decanted off and then stored at 4°C. I was under the impression that this could be stored and later used almost indefinately but two of four samples extracted several months back failed to produce a product (when it was known they should have).

Assuming no mistakes were made and the reactions were the same, is there a technical reason the template would degrade to an unusable point?

Is there a rule of thumb about how long it can reasonably be expected to last?

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My rule of thumb for DNA samples (in TE or water) - if I have plans to use it that week, I store at 4C. If I plan on using it within a month, I store at -20C. If I'm not sure when I will use it, I keep multiple aliquots at -80C. DNA can degrade by acid hydrolysis in water, because of contaminating nucleases in the sample, and by multiple freeze/thaw cycles.

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  • $\begingroup$ Is there any long term storage option at room temperature? biology.stackexchange.com/questions/2231/… -Thanks! $\endgroup$ – Registered User May 11 '12 at 12:28
  • $\begingroup$ DNA has a half-life of over 500 years under perfect circumstances. However, DNA degrades over time, and when kept in solution, it is difficult for there to be exactly 0 microbes, DNases or chemicals present which can hydrolyze the helix. It degrades over time and old DNA samples kept even at -20C very frequently show poorer results, especially when it is thawed repeatedly. Primers can also degrade gradually at room temperature, etc. $\endgroup$ – S Pr Aug 7 '18 at 13:10

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