GO consists of hierarchically structured vocabulary divided into three basic subcategories: molecular function, biological process and cellular component. Each term in GO is referred by an identifier of the form GO:xxxxxxx, a subcategory, and an associated textual description for that term. For example, the identifier GO:0019319 is of subcategory biological process and has short description as ‘hexose biosynthetic process’ (Figure).
GO organizes the terms in a directed acyclic graph (DAG) structure where terms are associated by is a or part of relationships. The is a classifier represents a subclass relationship where ‘A is a B’ means A is description of B but at higher depth or more narrower description. ‘A part of B’ indicates that whenever A is present it is part of B. A gene can be described as performing one or more molecular functions, being part of one or more biological process and located in one or more cellular components. Another important feature of GO is that it supports association of an evidence code with each annotation indicating the nature of evidence sources that are used to support that annotation. Examples of the evidence codes are IDA (Inferred from Direct Assay), which indicates that a direct assay was carried out to determine the function, and ISS (Inferred from Sequence or Structural Similarity), which clarifies that any analysis based on sequence alignment, structure comparison, or evaluation of sequence features such as composition is performed.
GO organizes the terms in a directed acyclic graph (DAG) structure where terms are associated by is a or part of relationships. The is a classifier represents a subclass relationship where ‘A is a B’ means A is description of B but at higher depth or more narrower description. ‘A part of B’ indicates that whenever A is present it is part of B. A gene can be described as performing one or more molecular functions, being part of one or more biological process and located in one or more cellular components. Another important feature of GO is that it supports association of an evidence code with each annotation indicating the nature of evidence sources that are used to support that annotation. Examples of the evidence codes are IDA (Inferred from Direct Assay), which indicates that a direct assay was carried out to determine the function, and ISS (Inferred from Sequence or Structural Similarity), which clarifies that any analysis based on sequence alignment, structure comparison, or evaluation of sequence features such as composition is performed.
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