Updated November 9, 2007
Used for annotations when information about the molecular function, biological process, or cellular component of the gene or gene product being annotated is not available.
Use of the ND evidence code indicates that the annotator at the contributing database found no information that allowed making an annotation to any term indicating specific knowledge from the ontology in question (molecular function, biological process, or cellular component) as of the date indicated. This code should be used only for annotations to the root terms, molecular function ; GO:0003674, biological process ; GO:0008150, or cellular component ; GO:0005575, which, when used in annotations, indicate that no knowledge is available about a gene product in that aspect of GO.
Annotations made with the ND evidence code should be accompanied by a reference that explains that curators looked but found no information. Note that some groups check only published literature while other groups also make sequence comparisons to see if an annotation can be made on the basis of a sequence comparison. The GO Reference collection includes a reference that can be used with ND when both literature and sequence have been checked; to use it, put "GO_REF:0000015" in the reference column of a gene association file.
Note that use of the ND evidence code with an annotation to one of the root nodes to indicate lack of knowledge in that aspect makes a statement about the lack of knowledge only with respect to that particular aspect of the ontology. Use of the ND evidence code to indicate lack of knowledge in one particular aspect does not make any statement about the availability of knowledge or evidence in the other GO aspects.
Even if an author states in a paper that there is no data available or nothing is known about the gene product in a particular GO aspect, annotation to the corresponding root node should be made with ND evidence code citing either the annotating group's internal reference or the GOC's reference on use of the ND evidence code, not a specific paper.
Note: The ND evidence code, unlike other evidence codes, should be considered as a code that indicates curation status/progress than as method used to derive an annotation.
When a gene product is annotated to a GO term using the NOT qualifier, this is a statement that it is not appropriate to associate that specific GO term with that particular gene product. However, such a negative annotation does not make any positive statements about the role of that gene product. Thus, there should always be a positive annotation, in addition to the NOT annotation. If nothing is known about the role of the gene product in a given aspect (molecular function, biological process, or cellular component) of GO, then the positive annotation should be made to the root node for that aspect using the ND evidence code.