In practice, the number of protein targets is below 819, since multi-component targets may be variably annotated against either a protein subunit, the complex target, or both. For example, probes directed against the BCR-ABL1 fusion protein may be annotated with the fusion protein (of which there are several length forms in TrEMBL but not Swiss-Prot) or ABL1 (P00519) or, in the case of ~20 probes from the Probe Miner set, BCR (P11274). Other complicating examples are the Cyclindependent kinases (CDKs), where the probes may be annotated by sources with one of the human CDKs, a CDK in complex with a specific Cyclin, or both.