Steps used by Blast algorithm
(b) In the later version of BLAST the method changed. The change is in the lower T value,
resulting in a longer words list.
The program looks for the word match first, then trys to locate several short words on the same diagonal, and then extends the alignment on both sides of the hits on the same diagonal, allowing short gaps.
The newly found diagonals are scored (sum of the scores of the individual matches).