OligoArrayDb, the Source of Microarray Probes for
Escherichia coli str. K12 substr. MG1655
Probe set created on 2009-09-16, updated on 2009-09-16.
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[Source of Commercial Oligonucleotide Microarrays for Escherichia coli str. K12 substr. MG1655]


The Escherichia coli str. K12 substr. MG1655 genome is provided in 1 piece of sequence ( U00096 ) representing a total of 4295 transcripts. These sequences have been analized for their GC content as this is an important parameter for probe design. The average GC content of these coding sequences is 51%, with a minimum and a maximum of 26% and 66% respectively. Ninety percent of these sequences have a GC content comprised between 41%and 56%. These values have been used to set OligoArray options during design. Here is the parameter set used for this particular design.

This database contains 12012 oligonucleotides to represent the Escherichia coli str. K12 substr. MG1655 transcriptome. Among these 12012 oligonucleotides, 11173 are considered to be fully specific to their targets according to the design parameters described above.  In other terms, this database provides oligonucleotides for 4250 transcripts and 4081 (95% of all sequences) have at least one specific oligo representing them. The figure below gives details on the number of CDS with specific probes.

Understanding this graph:
In the best case, you want the proportion of black and red genes to be as small as possible. Black ones are the genes with no probe at all. These genes will always be missing on your array. Red ones are the sequences for which OligoArray was not able to find a specific probes. However, it reported a non-specific probe. Our thresholds to define specific probes are quite conservative and many non-specific probes will actually prove to be specific in a real experiment. All other genes (blue, yellow and green) have at least one specific probe. While the number of genes with 3 specific probes may vary greatly from an organism to another, this may have little effect on your microarray design. Indeed, many will prefer to have one probe per gene, this probe being replicated several times on the array rather than having several probes per gene with less replicates.


Here we report the transcripts that do not have any oligonucleotide at all or any specific oligonucleotides.

With all these data in mind, you may want to access to the oligonucleotide page where you can download a microarray probe set representing the coding sequences of Escherichia coli str. K12 substr. MG1655.
 

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