Figure 1

An illustrative example of Gene Ontology (GO). An illustrative example of GO forming a directed acyclic graph (DAG), in which nodes and edges represent GO terms and "is-a" or "part-of" relationships between terms. {t₁, ..., t₇, root} is the set of GO terms, and {g₁, ..., g₁₀} is the set of genes annotated to these terms.