Blast search help needed.

Ewan Birney birney at sanger.ac.uk
Mon Oct 7 08:09:48 EST 1996


Chris Kafer wrote:
> 
> mperr1 at hamon.swmed.edu (Michael Perry) wrote:
> 
> Thanks for the reply but I tried that first.  What it appears to do is
> compare the entire sequence (as if it were a single ORF) in all 6
> frames.  What I would like to do is have it blast the real ORFs >30
> amino acids individually.  When I blast them  manually, it brings back
> different hits than a blastx search of the entire sequence.
> 
> As an example, when I blast one of the 200 aa ORFs it returns an EST
> clone.  When I blast the entire sequence, of which this ORF is just a
> part, it doesnt show up.  Hopefully I explained that clearly!
> 

You probably already realise this, but the fact that it comes
up in ones search and not the other is "meaningful" in the 
BLAST view: what you have done is 'manually' trim one sequence
to a region, specialising in one particular region, and therefore
hits against that region now get a lower probability of being
random. [what I am saying is that this is what you expect].

[now for the plug]:
Although it does not do all of what you want, PairWise and
SearchWise can run a DNA query against a protein database allowing
for Frameshifts and to a certain extent, introns. The DNA2DNA
approach which you want we are developing but it is not released
yet. You can get PairWise and SearchWise from

http://www.sanger.ac.uk/~birney/wise/topwise.html

ewan




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