<P> The "NCBI Bookshelf is a collection of freely accessible, downloadable, on - line versions of selected biomedical books . The Bookshelf covers a wide range of topics including molecular biology, biochemistry, cell biology, genetics, microbiology, disease states from a molecular and cellular point of view, research methods, and virology . Some of the books are online versions of previously published books, while others, such as Coffee Break, are written and edited by NCBI staff . The Bookshelf is a complement to the Entrez PubMed repository of peer - reviewed publication abstracts in that Bookshelf contents provide established perspectives on evolving areas of study and a context in which many disparate individual pieces of reported research can be organized . </P> <P> BLAST is an algorithm used for calculating sequence similarity between biological sequences such as nucleotide sequences of DNA and amino acid sequences of proteins . BLAST is a powerful tool for finding sequences similar to the query sequence within the same organism or in different organisms . It searches the query sequence on NCBI databases and servers and post the results back to the person's browser in chosen format . Input sequences to the BLAST are mostly in FASTA or Genbank format while output could be delivered in variety of formats such as HTML, XML formatting and plain text . HTML is the default output format for NCBI's web - page . Results for NCBI - BLAST are presented in graphical format with all the hits found, a table with sequence identifiers for the hits having scoring related data, along with the alignments for the sequence of interest and the hits received with analogous BLAST scores for these </P> <P> The Entrez Global Query Cross-Database Search System is used at NCBI for all the major databases such as Nucleotide and Protein Sequences, Protein Structures, PubMed, Taxonomy, Complete Genomes, OMIM, and several others . Entrez is both indexing and retrieval system having data from various sources for biomedical research . NCBI distributed the first version of Entrez in 1991, composed of nucleotide sequences from PDB and GenBank, protein sequences from SWISS - PROT, translated GenBank, PIR, PRF and PDB and associated abstracts and citations from PubMed . Entrez is specially designed to integrate the data from several different sources, databases and formats into a uniform information model and retrieval system which can efficiently retrieve that relevant references, sequences and structures . </P> <P> Gene has been implemented at NCBI to characterize and organize the information about genes . It serves as a major node in the nexus of genomic map, expression, sequence, protein function, structure and homology data . A unique GeneID is assigned to each gene record that can be followed through revision cycles . Gene records for known or predicted genes are established here and are demarcated by map positions or nucleotide sequence . Gene has several advantages over its predecessor, LocusLink, including, better integration with other databases in NCBI, broader taxonomic scope, and enhanced options for query and retrieval provided by Entrez system . </P>

What is genbank and what does it do