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Finds regions of local similarity between biological sequences. The program compares nucleotide or protein sequences to sequence databases and calculates the statistical significance of matches. BLAST can be used to infer functional and evolutionary relationships between sequences as well as to help identify members of gene families.

A searchable database of genes, focusing on genomes that have been completely sequenced and that have an active research community to contribute gene-specific data. Information includes nomenclature, chromosomal localization, gene products and their attributes (e.g., protein interactions), associated markers, phenotypes, interactions, and links to citations, sequences, variation details, maps, expression reports, homologs, protein domain content, and external databases.

A collection of nucleotide sequences from several sources, including GenBank, RefSeq, the Third Party Annotation (TPA) database, and PDB. Searching the Nucleotide Database will yield available results from each of its component databases.

The Protein database is a collection of sequences from several sources, including translations from annotated coding regions in GenBank, RefSeq and TPA, as well as records from SwissProt, PIR, PRF, and PDB. Protein sequences are the fundamental determinants of biological structure and function.

The Molecular Modeling Database (MMDB) contains 3D macromolecular structures, including proteins and polynucleotides. MMDB contains over 40,000 structures and is linked to the rest of the NCBI databases, including sequences, bibliographic citations, taxon.

In the process of being merged with the Nucleotide DB, see below.

The Conserved Domain Database (CDD) contains protein domain models imported from outside sources, such as Pfam and SMART, and curated at NCBI. CDD contains over 12,000 such models and is linked to other NCBI databases, including protein sequences, bibliog

The PDB archive contains information about experimentally-determined structures of proteins, nucleic acids, and complex assemblies.

This collection of related protein sequences (clusters) consists of Reference Sequence proteins encoded by complete genomes. This database contains both curated and non-curated clusters.

BLAST finds regions of similarity between biological sequences