[SagarikaGhosh]

Bioinformatics is the science concerned with the development and application of computer hardware and software to the acquisition, storage, analysis and visualization of biological information.

A database is a vast collection of data pertaining to a specific topic, e.g., nucleotide sequence, protein sequence etc., in an electronic environment. Databases are the heart of bioinformatics. There are a very large number of databases, which is growing rapidly.
The utilization of various databases requires the use of suitable search engines and analysis tools. These tools are often called database mining tools and the process of database utilization is known as database mining.

BLAST (Basic Local Alignment Search Tool) is a family of user-friendly sequence similarity search tools on the web. The BLASt server is supported through NCBI, USA. This tool is designed to identify potential homologues for a given sequence. It can analyze both DNA and protein sequences. Identification of homologues allows the prediction of potential functions and in modeling of the 3-D structure. A local alignment finds the optimal alignment between sub regions or local regions of the specified sequences. A local alignment search tool is used to find sequence motifs, domains, etc.

There are several BLAST programmes. Each of them serves as specific purpose. The different types of BLAST programmes are briefly described below. The new BLAST programmes are called BLAST 2.0.

1. BLASTp. It compares the submitted protein sequence against a protein database.
2. BLASTx. This programmes translates the submitted nucleotide sequence into amino acid sequence and compares the latter with a protein database.
3. BLASTn. This is used to compare a nucleotide sequence with a nucleotide sequence database.
4. tBLASTn. The programme converts the submitted protein sequence into nucleotide sequence and compares it with nucleotide sequence database.
5. tBLASTx. This programme translates the submitted nucleotide sequence as well as the nucleotide sequence database into amino acid sequences and searches for homology between the two.

ENTREZ. It is one of the most popular search engines at NCBI, USA. It searches bibliographic citations and biological data from a variety of reliable databases, viz., SWISS-PROT, PDB, GeneBank, and EMBL etc. It offers a variety of criteria of information, e.g., all possible citations from a given author that deal with a given subject that deal with a given subject, standard names for given genes, a given sequence database etc.