Fig. 1

Repeated extractions and qPCR plate runs enable observation of measurement variability. Four samples (A-D) of approximately 1 g were each split evenly by weight between 11 tubes. DNA was extracted from each of these 44 replicate samples using a robotic protocol. Each replicate sample was run in quadruplicate, on each of three plates. a Cts are shown on the Y-axis. The difference between the highest and the lowest of the Cts for these samples is 2.8, 2.3, 2.0 and 5.3, respectively. b Each Ct from (a) was converted into a DNA concentration (in ng/μl) using the standard curve on that plate. The ranges of DNA concentrations for these four samples were 0.11, 0.60, 1.3 and 0.0028, respectively