Hi Ross,
There are a few prior mailing list answers that can provide help. For 
each, substitute the dbSNP build to be "129" and the genome to be March 
2006 (hg18).

http://www.soe.ucsc.edu/pipermail/genome/2007-January/012650.html
General instructions for obtaining the SNP flanking sequence from the 
genomic. For you query, paste in the rs numbers into the identifiers 
filter and set region = genome, name file, and download locally. Click 
on "describe table schema" to understand formatting and other 
information linked to this data. Also extract the table to obtain 
variation(s). Note that the sequence output has the reference genome's 
sequence. You will need to swap in the SNP variation data for the SNP 
base position (sometimes this is a deletion) to create the variant fasta 
sequences using your own tools. Other SNP tracks will also contain data 
in this format and can be handled the same way. This is probably the 
best method to get all of the variation data.

http://www.soe.ucsc.edu/pipermail/genome/2008-June/016559.html
Genomic files in Downloads area with IUPAC substitutions for single-base 
SNPs only.
To extract specific regions from these genomic fasta files once you have 
them locally:
1) obtain coordinates of SNP(s) from Table browser and expand to be 200 
upstream and 200 downstream
2) use the utility faFrag to extract sequence (wrap in a shell/perl/etc. 
script).
This utility is in kent source tree. 
http://genomewiki.cse.ucsc.edu/index.php/Kent_source_utilities

Help/FAQ links:
http://genome.ucsc.edu/goldenPath/help/hgTablesHelp.html
http://genome.ucsc.edu/FAQ/FAQdownloads#download1
http://genome.ucsc.edu/FAQ/FAQdownloads#download27
http://genomewiki.ucsc.edu/index.php/Coordinate_Transforms

Jennifer Jackson
UCSC Genome Bioinformatics Group
Ross KK Leung wrote:
> Dear all,
>
> We would like to retrieve flanking sequences at UCSC site, e.g. for
> rs17019583: 200 bases upstream, and 200 downstream for a total of 401 bases.
> And then save as txt files.
>
> How can we do that in batch if we have dozens of rs numbers in hand? Thanks
> a lot for your advice.
>
> Best regards, Ross
>
>
>
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