BLAST![](../gifs/yellow.gif)
(Basic Local Alignment Search Tool) is a set of similarity search programs designed to explore all of the available sequence databases regardless of whether the query is protein or DNA. The
BLAST![](../gifs/yellow.gif)
programs have been designed for speed, with a minimal sacrifice of sensitivity to distant sequence relationships. The scores assigned in a
BLAST![](../gifs/yellow.gif)
search have a well-defined statistical interpretation, making real matches easier to distinguish from random background hits.
BLAST![](../gifs/yellow.gif)
uses a heuristic algorithm which seeks local as opposed to global alignments and is, therefore, able to detect relationships among sequences which share only isolated regions of similarity (
Altschul et al., 1990![](../gifs/red.gif)
).