Statistical significance of the transcription factor activities. Most of the strongly periodic activity profiles (log10(TFA)) of the 36 selected TFs have a single dominant frequency of oscillation. The x-axis marks the different Fourier frequencies and the y-axis represents the Average Periodogram . Clearly the dominant Fourier frequency, marked by a spike, is very prominent in every TF, and is indicative of its strongly periodic profile. Further, the similarity among the locations of the spikes across all 36 TFs shows their regulation by common cell cycle processes. Also see Table 1 for the related p-values that measure the periodicity of each profile.