The application may refer to a biological sequence belonging to the state of the art by merely providing the sequence's accession number in a publicly available database, without presenting the sequence itself either in a sequence listing complying with WIPO Standard ST.25 or in any other format.
Since in this case the sequence is already publicly available, the applicant does not need to supply a sequence listing, unless these prior art sequences are referred to in the claims or constitute essential features of the invention or are required for the search. In this latter case such sequences should be included in the sequence listing at the time of filing (see Notice from the European Patent Office dated 28 April 2011, OJ EPO 2011, 376), also in order to avoid potential substantive problems. If the database and/or the sequences in question is/are not completely and unambiguously identified, the sequences are not sufficiently disclosed according to Art. 83 and cannot be added to the application to complete the disclosure without contravening Art. 123(2) (see F-III, 2).
If such insufficiently disclosed sequences are not essential features of the claimed invention, the examiner will normally raise no objection. On the other hand, where these sequences are essential features of at least a part of the claimed subject-matter, this results in problems relating to the sufficiency of the original disclosure according to Art. 83 because the nature of the sequences cannot be unambiguously derived from the incomplete or ambiguous reference to the database.
Examples where a biological sequence is considered an essential feature of the invention would be a diagnostic method using a particular nucleic acid sequence or a product made by a biochemical process using an enzyme with a particular amino acid sequence. An example of ambiguous identification would be the citation of an accession number of a certain protein in the database of the European Molecular Biology Laboratory EMBL with no indication of which version number or database release number is meant when there are several such numbers referring to different sequences of the protein.