A novel technique for isolating DNA from Tempus™ blood RNA tubes after RNA isolation

We use Tempus blood RNA tubes (Applied Biosystems) during health assessments of American moose (Alces alces spp.) as a minimally invasive means to obtain RNA. Here we describe a novel protocol to additionally isolate high-quality DNA from the supernatant remaining after the RNA isolation methodology. Metrics used to qualify DNA quality included measuring the concentration, obtaining a DNA integrity number from a genomic DNA ScreenTape assay (Agilent), and running the isolated DNA on an agarose gel. Of the 23 samples analyzed, the average DNA concentration was 121 ng/µl (range 4-337 ng/µl) and a genomic DNA ScreenTape assay of seven samples indicated high DNA integrity values for 6 of the 7 samples (range 9.1-9.4 out of 10). Of the DNA sent for genotyping by sequencing, all proved to be of sufficient integrity to yield high-quality next-generation sequence results. We recommend this simple procedure to maximize the yield of both RNA and DNA from blood samples.