Let's assume that we found out that gene G can be labeled with the Gene Ontology term T. In the Gene Ontology T has 4 children T0, T1, T2, T3, each connected with term T through a "is a" relationship.
Can we infer that since gene G is labeled as term T, it also has to be one of the child terms T0, ..., T3? In other words, is the Gene ontology complete in the sense that the child terms of a term T list all possible more specific functions / processes / components of T? So any time that term T is present, at least one (or maybe exactly one?) of its child terms has to be present?
Ontology is DAG. In general (in most of the cases), child inherits parent term, not the other way around i.e gene with T0 term is also classified T term, but a gene with T term may not be assigned T0. In short T is superset of T0..T3..Tn.