Surprising stability of DNA in stains at extreme humidity and temperature

Abstract

The stability of DNA in air-dried blood and buccal stains at various conditions of relative humidity and temperature was tested by the ability to amplify 1600 and 273 bp DNA fragments by PCR and a 147 bp DNA fragment by real time PCR. Surprisingly it was observed that even the long DNA fragment was amplifiable after incubation for more than 1 month at 100% humidity and temperatures up to 65 °C. The 273 bp fragment was amplifiable after 3 months at 65 °C, 100% humidity. Fungal/microbial growth was observed on some stains after incubation at room temperature or 35 °C at 100% humidity, but never at lower humidity. However, in wet stains DNA degraded rapidly. Thus, even at extreme humid and hot conditions simple air-drying is adequate for the preservation for month of stains and reference samples to be analysed for STRs and SNPs.