The GO knowledgebase consists of three main components: the GO ontology, the standard GO annotations, and the GO-Causal Activity Models (GO-CAMs) (2). In addition, GO develops tools (see GO toolset) to help users apply the GO knowledgebase in their analyses (3–5). The GO ontology provides a formal structure that defines the universe of possible gene functions (GO terms), and the relationships between them (6). Standard GO annotations are assertions that relate a specific gene with a specific ontology term describing its function, along with the evidence for that assertion (7). GO-CAMs are a relatively new component in the GO resource (2). GO-CAMs link multiple standard GO annotations into a more comprehensive model of gene function and allow causal influences between molecular activities to be detailed using relations from the Relation Ontology (https://github.com/oborel/obo-relations). GO-CAMs currently are of two main types: those that include causal influences between activities (e.g. a biological pathway), and those that do not.
