Unsupervised hierarchical clustering of the patterns of variation in expression for 9,259 genes (represented by 16,959 cDNA) in 80 pancreatic tissue specimens (A). The image uses a color code to represent relative expression levels. Red represents expression levels greater than the mean for a given gene across all samples. Green represents expression levels less than the mean across samples. A color bar (top) relates color code to the magnitude of the differences in gene expression relative to the all-sample means for each gene. Grey indicates missing or excluded data. (B) Image representing gene expression in pancreatic cell lines, primary pancreatic duct and islet cells, normal pancreas, and adenocarcinomas. The cell lines and amplified samples were each mean-centered separately. The genes presented are organized and displayed in an identical manner to the genes shown in panel (A). (C) Enlarged view of the array dendrogram shown in panel A along with sample identification.