The Yeast and Arabidopsis specific BLAST WWW server has been modified
to use the "dust" filter by default for nucleic acid query
sequences. The dust filter masks out simple repeat and high AT rich
regions from the query sequence. The resulting sequences contains Ns
at the masked positions. This masking or filtering allow the search to
go faster and generally report more interesting hits. With all the
simple repeats removed you can more easily see hits of the unique
regions of your sequence. If however you wish to turn the filtering
off just select "none" from the Filter Options menu on the BLAST form.
