The Affymetrix sub-cluster sequences are the building blocks of probe selection. In other words, an Affymetrix sub-cluster is a group of sequences all representing the same transcript, denoted by the transcript ID field in a Target Databank record. The sub-cluster databanks, in the NetAffx™ Analysis Center, provide a list of all the accession numbers of the public sequences used for probe selection. Sub-cluster databanks may also be queried with accession numbers to identify your favorite genes on GeneChip® arrays. Use the sub-cluster information to precisely identify the correlation of probes with your favorite EST or mRNA sequences in public databases. This analysis is also relevant in the interpretation of GeneChip® expression results.