Fig. 12.

Hierarchical cluster analysis of temporal expression profiles of major drug-processing genes. Each column represents a circadian time point, and each row represents a gene with the name indicated. The number in parentheses beside each gene name represents the mRNA expression peak/trough ratio of that particular gene. Numbers at the top depict the time of day, and the bar represents the light phase (white) or dark phase (black). Peak expression for each gene is represented by the darkest region of the gray scale spectrum and lowest expression indicated by the lightest (gray) region. Each spectrum is specific to the scale of mRNA expression for each gene on an individual basis. Therefore, comparing gene expression profiles across gray scale spectra is not valid because of differences in the relative gene expression.