New Database and View Options for Nucleotide BLAST Services
The nucleotide-nucleotide BLAST pages linked to the BLAST homepage now offer the human and mouse transcript and genomic reference sequences as database options (Figure 1).
Click on image to view larger
Figure 1. New database and display options for NCBI Web BLAST services. A. The human and mouse genomic and transcript databases can now be selected using the radio buttons on the BLAST form. The traditional BLAST databases are available through the pull-down list once the "Others (nr etc.)" radio button is selected. B. The improved display with the sorting capabilities is invoked through the "New View" checkbox that is now selected by default on the "Format" section of the nucleotide BLAST forms.
A new output display for all searches provides a more organized presentation of the search results and has powerful new sorting options (Figure 2).
Click on image to view larger
Figure 2. New BLAST output display. The results of a search with the crab-eating macaque (Macaca fascicularis) CDC20 mRNA (AB168636) against the default human genomic plus transcript database.
A. The descriptions section of the output is a table with separate sections for Transcripts and Genomic Sequences. The search finds the corresponding human RefSeq transcript. It also finds matches to chromosomes 9 and 1 in both the reference and alternate assemblies of the human genome. The local metrics, E value and Max Score, identify the best match as the retrocopy psuedogene on chromosome 9. The intronless structure of the pseudogene gives a single high-scoring match. The total score metric makes it easy to find the functional eleven-exon gene on chromosome 1 even though the small individual exon matches give lower scores than the pseudogene. B. The alignment of the macaque mRNA to a contig on chromosome 1 from the reference human genome. Segments are sorted by "Query start position" to show the matches to the exons in order of position rather than E-value. C. Alignments displayed in the human map viewer are available by following the linked genomic sequence identifiers.
In addition to the traditional sorting by Expect Value, results can now be sorted by Maximum Score, Total Score, Percent Query Coverage, and Maximum Percent Identity. The Box below provides definitions for these metrics. Sorting options are also available for multiple hits within the alignments for each subject (database) sequence with the additional option of sorting by query or subject position-an option especially useful for ordering potential exons on genomic matches (Figure 2 B). Matches to genomic sequences in the new genome and transcript databases can now be displayed in the mouse and human Map Viewers as with the specialized genomic BLAST services (Figure 2 C).
These new database and display options provide rapid access to the most popular annotated genomes at the NCBI and expand the power of BLAST as a genome annotation tool.