Approach used in categorizer to assign genes to categories. A. Three steps used in the categorization process: (i) Information content calculation, (ii) semantic similarity score calculations for parent–child pairs and (iii) categorization according to the semantic similarity scores. See the main text for details. B. Illustrative (synthetic) example for the calculation of semantic similarity scores. Information content scores (I) are shown for each GO term. G0 is a root term. In this example, a user defined two categories (A and B) and assigned G22 to category A (orange), and G23 to category B (blue). Semantic similarity scores (S) of several terms are also shown.