question about affy microarray annotation on UCSC

[tujchl]

HI,
To my knockledge, microarry use short probe to detect mRNA level, So the sequence of probe should be very short. However the annotation of U133 plus2 or others on UCSC genome browser can be very long just like probe 204858_x_at below
some one can tell me why?
thanks
[IMG]http://b271.photo.store.qq.com/psb?/3ef3f4ff-5ea7-4eaa-bdcd-5b6fa2dad201/jvWZ*fq6e6BIegcjMcID3NQ*Q9ZCeYoivLgG5u6D6YY!/b/dHOVkKFGIAAA&bo=IAN7AAAAAAADAH0![/IMG]

[mastal]

Hi tujchi,

Affymetrix microarray probes are usually 25 bp long.

However, the annotations for affymetrix arrays may include the part of the gene/transcript that the set of probes for a probe set were taken from, or the gene/transcript that the probe/probe set is assigned to, which would be a much longer sequence than just one of the probes.

If you are lookig for the probe sequences, you can find them on the Affymetrix web site, especially on the NetAffx analysis centre,

http://www.affymetrix.com/analysis/index.affx

and if you have more questions about microarrays you should try posting them to the Bioconductor mailing list:

http://www.bioconductor.org/