New ribosomal RNA BLAST databases available on the web BLAST service and for download

We have a curated set of ribosomal RNA (rRNA)  reference sequences (Targeted Loci) with verifiable organism sources and current names. This set is critical for correctly identifying and classifying prokaryotic (bacteria and archaea) and fungal samples (Table 1). To provide easy access to these sequences, we recently added a separate rRNA/ITS databases section on the nucleotide BLAST page for these targeted sequences that makes it convenient to quickly identify source organisms (Figure 1)

Database BioProjects Sequences
16S ribosomal RNA (Bacteria and Archaea) PRJNA33317 , PRJNA33175


18S ribosomal RNA sequences (SSU) from Fungi type and reference material PRJNA39195 2,337
28S ribosomal RNA sequences (LSU) from Fungi type and reference material PRJNA51803 5,185
Internal transcribed spacer region (ITS) from Fungi and Oomycete type and reference material PRJNA177353, PRJNA362621



Table 1.  NCBI curated targeted rRNA sequences now available as BLAST databases. Continue reading

NCBI Replacing Obsolete NCBI Genomes (chromosome) and Removing Human ALU repeat elements (alu_repeats) BLAST databases

NCBI will discontinue both the NCBI Genomes (chromosome) and the Human ALU repeat elements (alu_repeats) BLAST databases in October 2017.

Better alternatives to NCBI Genomes (chromosome)

The existing NCBI Genomes (chromosome) database does not offer complete and non-redundant coverage of genome data. The newly added NCBI RefSeq Genomes Database (refseq_genomes) and the RefSeq Representative Genomes Database (refseq_representative_genomes) are more useful alternatives to the chromosome database. You can select these databases from the database pull-down list on any general BLAST form that searches a nucleotide database (blastn, tblastn).

nucleotide-nucleotide BLAST database menu

Figure 1. The nucleotide-nucleotide BLAST database menu with the recommended (RefSeq Genome and Representative genomes) and deprecated (NCBI genomes (chromosomes) and Human ALU repeats) databases highlighted.

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Troubleshooting GenBank Submissions: Annotating the Coding Region (CDS)

This article is intended for GenBank data submitters with a basic knowledge of BLAST who submit sequence data from protein-coding genes.

One of the most common problems when submitting DNA or RNA sequence data from protein-coding genes to GenBank is failing to add information about the coding region (often abbreviated as CDS) or incorrectly defining the CDS. Incomplete or incorrect CDS information will prevent you from having accession numbers assigned to your submission data set, but there is a procedure that will help you troubleshoot any problems with the CDS feature annotation: doing a BLAST analysis with your sequences before you submit your data.

NOTE: We have changed BLAST search results displays since publishing this blog. For updated guidance on using Nucleotide BLAST (blastn) to help you troubleshoot coding region annotation, see the articles in the  NCBI Support Center.

Here’s how to use nucleotide BLAST (blastn) and the formatting options menu to analyze, interpret and troubleshoot your submissions:

1. To start the BLAST analysis, go to the BLAST homepage and select “nucleotide blast”.

nucleotide blast link. click to start BLAST analysis

Figure 1. Select “nucleotide blast”.

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