Figure 6. The Number of Genes Peaking during each portion of the Cell Cycle.

The cell cycle was divided into 45 consecutive portions, or bins. If the cell cycle is considered as a circle of 360o, then each bin occupies 8o. Every gene was analyzed using a Fourier transform to determine the time of peak expression in elutriation A, from 0o to 360o. The number of genes peaking in each bin was summed, and plotted (grey bars, background), with the number of genes in each bin shown on the y-axis. Genes in specific clusters are shown by colored bars (foreground). The Fourier transform calculation was similarly used to derive the time of peak septation and peak binucleate cells (from Figure 1) and these cell cycle landmarks are indicated.

A. The top 750 cell cycle regulated genes were analyzed for time of peak expression. Genes from different clusters are stacked when they occur in the same bin.

B. All genes (~5000) were analyzed for time of peak expression, exactly as in A.

C. The bottom 4000 genes were analyzed for time of peak expression. Data was extracted from arrays before the red/green normalization step, so that the bottom 4000 genes would not be affected by the normalization and the cyclic expression of the top 750 genes.

D. All genes (~5,000) were analyzed for time of peak expression after gene-wise random shuffling of microarray observations. This randomization serves as a negative control for the Fourier calculation in parts A, B, and C.