PO Annotation Extensions (column 16)

Column 16 should be used when the appropriated relation is not specified or cannot be inferred within the PO, for example, for creating specific part_of relations when only a general part_of relation exists (see example 1), for linking a structure to a specific growth or developmental stage, when that link does not already exist or cannot be inferred (example 2), for specifying spacial relations that may be present in the experiment being annotated, but that are not specified in the PO (example 3). See the documentation on using the annotation extension column for details of practical usage; a wider discussion of the annotation extension column can be found on the GO wiki.