Schema of the centric approach in ortholog-linked database building and putative ortholog detection. (a) An example of putative ortholog creation for the ornithine decarboxylase 1 (ODC-1) gene. U74A and U34A probe IDs were EGO orthologs (solid line) for the U133A and U95A ODC-1 gene but were not directly linked (dashed line) either in EGO or in the Affymetrix ortholog table. (b) The reference genes common to all arrays (see Figure 1) and their corresponding orthologs for U95A-U74A, U95A-U34A, and U74A-U34A pairs were permutated and all possible combinations counted (dashed lines). EGO combinations were retrieved from RESOURCERER-generated tables for these paired arrays and counted (solid lines). The difference in the predicted and existing pairs represents the number of putative orthologs to be created, based on homology to the common reference gene.