Sequence Revision History Page Offers New Comparison Functions

Changes in records from the Entrez Nucleotide and Protein databases can now be visualized using the Sequence Revision History tool at:

To retrieve the history of a record, one can enter the accession number, the GI number, or the FASTA-style SeqID of that record into the query box at the top of the page. Figure 1 shows the revision history table for the nucleotide sequence AF123456. The table displays the dates of changes made to the record since it was first released. The first two columns contain, respectively, the GI numbers and the version numbers of the sequence, which are only changed if the sequence data itself has been modified. Updates to any record may include changes to the sequence, publication information, or annotations made by the authors. In this case, the sequence data has been modified once. The “Update Date”, identical to the “Modification Date” seen on the Entrez Limits page, is the date that appears in the upper right hand corner in the flat file view of Entrez records. The “Status” column indicates the most recently-updated version of the record, the “Live” record, that is retrievable from Entrez; the older versions have a status of “Dead”. The date the record was first seen at NCBI is given at the bottom of the table.

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Figure 1. The Sequence Revision History table for AF123456. The last two versions of the record have been selected for comparison.

The last two columns are labeled I and II, respectively, and are used to select the two versions of the record to compare. One can view the differences in several display formats, including GenBank/GenPept flat file, XML, and ASN.1. The differences between the records are highlighted in color, as shown in Figure 2. The “GenBank diff” format lists the differences in the manner of the UNIX “diff” command, without highlighting. The FASTA and BLAST formats can be used to pinpoint differences in the sequence data.—VP

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Figure 2. GenBank display of the differences between two versions of AF123456. Sections of the record in which there are differences are shown for each version and highlighted.