What's the meaning behind the Affy microarray probe ID order?

Question

[ZHANG Li]

Hi everyone,

I have downloaded a dataset about Affymetrix gene expression from GEO, and I found that the probes ID are listed like:

171720_x_at

171721_x_at

171722_x_at

171723_x_at

171724_x_at

171725_x_at

171726_x_at

......

and each of them is followed by the expression value. I know that all these probe ID can be converted to gene names. But my question is what's the meaning of the probe ID order? Why they are sorted like this and what's the meaning behind the sorting? I have tried to convert all probe IDs into gene symbols but can't find a clue about why they should be sorted in this way. It's like a random arrangement but I can't find any evidence either.

Thank you.

Answer 1

[mastal511]

There is no meaning to the microarray IDs. Probesets are designed by clustering mRNAs, cDNAs and ESTs for the species of interest. Sometimes the probe IDs might have the same ID as the UniGene cluster ID that the probeset was based on.

[ZHANG Li]

Thank you very much! I am quite new in this field. So...can this be understood as the measured genes are generally organized randomly?