Ontology Documentation

The Gene Ontology defines the universe of concepts relating to gene functions (‘GO terms’), and how these functions are related to each other (‘relations’). It is constantly revised and expanded as biological knowledge accumulates.


  • GO annotations: Gene association files submitted by members of the Gene Ontology Consortium
  • Ontology: Various versions of Gene Ontology
  • Mappings: Mappings from the GO to a number of external vocabularies also built for genome annotation

GO Annotation File Format 2.0

Annotation data is submitted to the GO Consortium in the form of Gene Association Format, or GAFs. This guide lays out the format specifications for GAF 2.0; for the older GAF 1.0 file syntax, please see the GAF 1.0 file format guide.

Please see the information on the changes in GAF 2.0.

General information about annotation can be found in the GO annotation guide.

LEAD Database Downloads

The GO database, accessed by tools such as AmiGO, contains ontology, gene product, sequence, and manual annotation data. It is available in a number of formats and configurations. This page details the database downloads available; for more information on the database itself, please see the GO database guide.

Download Mappings

Mappings of External Classification Systems to GO

The Gene Ontology is not the only attempt to build structured controlled vocabularies for genome annotation. To aid users, the GO Consortium provides mappings of its terms to those in a number of external vocabularies.