BLAST Search main parameters
- DESCRIPTIONS
- Restricts the number of short descriptions of matching
sequences reported to the number specified; default
limit is 100 descriptions. See also EXPECT.
- ALIGNMENTS
- Restricts database sequences to the number specified for
which high-scoring segment pairs (HSPs) are reported;
the default limit is 100. If more database sequences
than this happen to satisfy the statistical
significance threshold for reporting (see EXPECT below),
only the matches ascribed the greatest statistical
significance are reported.
- EXPECT
- The statistical significance threshold for reporting
matches against database sequences; the default value
is 10, such that 10 matches are expected to be found
merely by chance, according to the stochastic model
of Karlin and Altschul (1990). If the statistical
significance ascribed to a match is greater than the
EXPECT threshold, the match will not be reported.
Lower EXPECT thresholds are more stringent, leading
to fewer chance matches being reported. Fractional
values are acceptable.