Fig. 5
From: Statistical analysis of fractionation resistance by functional category and expression
Example of nested structure of GO terms. Starting at a low-level GO term “protein secretion”, it is inherited by two higher GO terms “secretion by cell” and “protein transport”. After a few more levels of GO terms (represented by dashed lines), the starting GO term is now inheriting two high level terms “cellular process” and “localization”. These high level terms are then linked to the root term, “biological process”. There are three root terms in gene ontology, they are “biological process”, “cellular component”, and “molecular function” [27]