The structure of the Gene Ontology (GO) is illustrated on a subset of the paths of the term “regulation of cell projection assembly,” GO:0060491, to its root term. The GO is a directed graph with terms as nodes and relationships as edges; these relationships are either is_a, part_of, has_part, or regulates. In its basic representation, there should be no cycles in this graph, and we can therefore establish parent (more general) and child (more specific) terms (see Chap. XX for more details on the different representations; cross-reference to Moni’s chapter). Note that it is possible for a term to have multiple parents. This figure is based on the visualization available from the AmiGO browser, generated on November 6, 2015. (3).