Two-way hierarchical clustering of the biological samples and the extracted genes. Log10 transformed gene expression ratio values of the 82 genes from the prototypes of the clusters of the biological samples were subjected to agglomerative hierarchical clustering as detailed in Figure 5. The resulting gene expression heat map contains the genes as the rows and samples as the columns with red indicating up regulation, green denoting down regulation and black signifying no change. At the top of the heat map, the level (UI/L) of ALT is plotted for each sample. At the bottom of the heat map, the severity of centrilobular necrosis observed is shown for each sample. (yellow, none; blue, minimal; magenta, mild; green, moderate).