Question: Humanht-12 V3 Expression Beadchip: How To Calculate Expression Of A Gene Having More Than One Mapped Probes?
gravatar for Ttnguyen
7.1 years ago by
Ttnguyen70 wrote:

Anyone knows how? Should I take the average of all probes mapped to that gene?

gene • 2.1k views
ADD COMMENTlink modified 7.0 years ago by rowland.mosbergen0 • written 7.1 years ago by Ttnguyen70
gravatar for Neilfws
7.1 years ago by
Sydney, Australia
Neilfws48k wrote:

For other platforms, gene-level summaries generally use the median of probes, not the mean. You might also use a procedure called median polish.

ADD COMMENTlink written 7.1 years ago by Neilfws48k
gravatar for Mark Dunning
7.1 years ago by
Mark Dunning20
Cambridge, Uk
Mark Dunning20 wrote:


Perhaps you can clarify what you mean by probes targeting the same genes? With the Illumina technology you have multiple (~20) beads that have the same probe sequence and these are known as a 'bead-type'. Combining beads for the same bead-type is done automatically for you in GenomeStudio, or in beadarray with the summarize function.

A gene can have multiple bead-types targeting it. However, averaging bead-types that target the same gene isn't really recommended for Illumina data. When a gene has multiple bead-types targeting it, the bead-types can target different isoforms of the same gene. Some isoforms might not be expressed (or have badly-designed probe sequences), so by averaging you would be diluting the signal of those isoforms that are expressed. If you want to have the data on a per-gene basis, I tend to pick the 'best' probe for each gene using a criteria such as the probe with the highest IQR. Or for a differential expression analysis should as limma, I would fit the model to all probes (probably after some filtering to remove non-informative probes) and then map to genes afterwards.

Hope this helps,


ADD COMMENTlink written 7.1 years ago by Mark Dunning20

Hi Mark, thanks a lot for your answer. Based on your explanation, I think bead-type would be more suitable word to say than probe.

ADD REPLYlink written 7.1 years ago by Ttnguyen70
gravatar for rowland.mosbergen
7.0 years ago by
rowland.mosbergen0 wrote:

I have been trained to show all the probes for that gene with the gene name next to it:


ADD COMMENTlink written 7.0 years ago by rowland.mosbergen0
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