3. Blast and the heuristic search of genetic information Flashcards
What is BLAST?
Basic Local Alignment Search Tool
It is a heuristic tool that uses dynamic programming to estimate the best match for a DNA or protein sequence without considering every possible alignment. It will not always find the best solution, but it will always find a good solution.
In a BLAST search, which sequence is considered the ‘query’?
The sequence that is subjected to comparison is the query (BLAST will search for this sequence against the sequences in the database). The sequence of interest
How does BLAST search for matches?
It takes a fragment from the query sequence - word - and compares it to fragments of subject sequences. Once it finds these ‘seeds’ it extends to both sides to see if there is a match. If we want to search for higher similarity sequences, we increase the word size.
