BLAST-N of low quality long sequences

blastall -p blastn -V T -F F -e 1e-20 -y 50 -X 75 -Z 500 -b 240 -v 240 -d DATABASE -i INPUT -o OUTPUT

Where:

-y X  dropoff value for ungapped extensions in bits (0.0 invokes default behavior)

      blastn 20, megablast 10, all others 7 [Real]

-X X  dropoff value for gapped alignment (in bits) (zero invokes default behavior)

      blastn 30, megablast 20, tblastx 0, all others 15 [Integer]

-Z X  dropoff value for final gapped alignment in bits (0.0 invokes default behavior)

      blastn/megablast 100, tblastx 0, all others 25 [Integer]