Example portion of the MP, and the equivalence relations between MP classes and EQ descriptions. Paths to the root over is_a links from 'Purkinje cell degeneration' and siblings. The is_a hierarchy is used for query-answering and genotype-phenotype analysis. Queries for 'neurodegeneration' or 'abnormal neuron morphology' should return genes or genotypes associated with 'Purkinje cell degeneration', such as the Pten gene. Note that prior to December 2008 MP lacked the highlighted link (indicated with the asterisk between two bold boxes), which resulted in false negatives for queries to 'neurodegeneration'. Using automated reasoning we were able to infer this link from the logical definitions and associated ontologies. We presented our results to the MP editors, who subsequently amended the ontology to include the link.