Figure 4. Library comparison. A: EST data for pairs of cDNA libraries can be selected for comparison. B: The output lists the genes identified in the first library, ranked by number and frequency of ESTs, and shows the number and frequency of ESTs for the same gene in the second library. This provides useful comparisons for relatively abundant transcripts in unnormalized (native abundance) cDNA libraries. For the same species (e.g., human retina versus human retinal pigment epithelium), libraries are compared based on common Entrez Gene IDs. Different species for which orthologous GeneIDs are linked through Homologene, can be compared (e.g., human retina versus mouse retina).