Oscillation of the unprocessed total signal.A) Prior to any pre-processing, the mean transcript abundance for all genes on the chip (blue dashed) and all 3347 protein-coding genes (black solid) exhibits diurnal oscillations. Significantly oscillating genes (posc<0.05) resemble the oscillation of the total intensity (black dotted), whereas the non-significantly oscillating genes (posc>0.05) show increased expression over the day and a peak at 17.5 CT (gray dashed). B) The majority of genes exhibit a phase angle ϕ in the range of 250−350 corresponding to expression over the day. C) The histogram of Spearman correlation coefficients γ between all pairwise combinations of the 3447 protein coding genes shows that most genes strongly correlate. Only a small amount of pairs is uncorrelated or anti-correlated.
Lehmann et al. BMC Bioinformatics 2013 14:133 doi:10.1186/1471-2105-14-133