Low Complexity Filter
Mask off segments of the query sequence that have low compositional complexity. Low complexity regions commonly give spuriously high scores that reflect compositional bias rather than significant position-by-position alignment. Filtering can elminate these potentially confounding matches (e.g., hits against proline-rich regions or poly-A tails) from the blast reports, leaving regions whose blast statistics reflect the specificity of their pairwise alignment. Queries searched with the blastn program are filtered with DUST. Other programs use SEG.