Somatic cell genomes of ALS patients have variable number of GGGGCC repeats in the C9ORF72 locus. Two sections of the same Southern blot (see raw image in Additional file 2: Figure S1) show hybridisation of EcoRI and XbaI digested DNA extracted from peripheral blood, cerebellum and cerebral cortex of two patients positive for GGGGCC repeat expansion. The ratios of the 1.33 kb to 1.05 kb bands intensities are shown below the image. Note that in this case these ratios are unconventionally high, which is due to the gel has been run for too long and therefore the 1.05 kb bands appeared too close to the edge of the gel, resulting in less efficient transfer and hybridisation of this band. However, the ratio for normal DNA sample is still approximately twice as high as the ratio for all DNA samples with GGGGCC repeat expansion.