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What is the pBR322 convention? For example in the description of the pET28a vector we can find information that the sequence is numbered by the pBR322 convention, so the T7 expression region is reversed on the circular map.

Alan Boyd
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Ala
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  • Could you please clarify the question? what do you mean by pBR322 convention? do you mean why it was named pBR322? I'm not clear what you mean by pET28a being numbered by the pBR322 convention. – Behzad Rowshanravan Jul 04 '14 at 23:26

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pBR322 is a distant ancestor of pET28a. If you compare the two maps below you will see that they have the same replicon labelled as ori or pBR322_origin.

The map of pBR322 is shown in the conventional orientation: the single EcoRI site is at coordinate 0/4359 and numbering proceeds in a clockwise direction through the BamHI site. The map of pET28a is presented with the pBR322-derived ori element in the same orientation (note the labelling of a pBRrevBam_primer also). Because of the way that the pET vectors were built, this means that in the conventional depiction the expression region runs counter-clockwise.

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Alan Boyd
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