View source for BLAST

==Basic Information==

{| style="float: right; border: 1px solid #BBB; margin: .46em 0 0 .2em;"
! Author
| Stephen Altschul, Warren Gish, David Lipman
|-
! Year
| 1990
|-
! Reference
| [http://www.ncbi.nlm.nih.gov/pubmed/2231712?dopt=Citation Basic local alignment search tool]
|-
! Short description
| Alignment Heuristic
|-
! Method
| seed words
|}

BLAST, Basic Local Alignment Search Tool, finds regions of local similarity between sequences. The program compares nucleotide or protein sequences to sequence databases and calculates the statistical significance of matches. BLAST is a heuristic to the calculation of optimal alignments calculated by dynamic programming.

==Details==

In a first step BLAST locates short words, with significant scores and a certain length (e.g. 3) within a sequence, this is called seeding. These first matches are used for local alignments. High scoring words within a database can be pre-calculated. The challenge of BLAST was to calculate proper statistics for the searches.