Sarcoplasmic reticulum GO node. As an example, the cellular component 'sarcoplasmic reticulum' is shown before (Panel A) and after (Panel B) the modifications described in this paper. Previously, the term sarcoplasmic reticulum had no specific child terms, therefore all annotations of the gene products known to act in specific regions or sub-types of the sarcoplasmic reticulum had to be made directly to the parent term. As a part of our work we added new terms to describe various regions and sub-types. As a result, the gene products previously annotated directly to sarcoplasmic reticulum can now be annotated to the more specific child terms giving far better reasoning power for analysis of high-throughput experiments. Black lines marked 'is_a' indicate the is_a relationship. Black lines marked 'part_of' indicate the 'part_of' relationship. Red lines indicate annotation of a gene product to a GO cellular component term. Annotation of a gene product to a GO cellular component term indicates that the gene product acts in the cellular location represented by the GO term.