Index (Barcode) Lengths - Are they ALL Even?

[cement_head]

Are all index/barcodes of EVEN length? For example, 6 bp, 8 bp, 10 bp, 12 bp?

Has anyone ever come across ODD index lengths? 5 bp, 7 bp?

I can't recall ever seeing a commercial kit with a barcode that has an odd number of bp. If I am correct, is there a reason for this?

Thanks

[cmbetts]

I can't speak for why Illumina hasn't done it, but at the companies I've worked at, we kept it at six or eight for Illumina compatibility.
Since almost all of Illumina's kits use six or eight, it's much easier to set up a run to do that length using basespace or experiment manager.
There's also the plain ol' inertia. Why test and validate new five or seven bp indexes when six and eight are working well enough and it's easy to find precalculated six and eight bp indexes with good color balance and hamming distance?

[cement_head]

Ok, good to know. There's more information here: http://journals.plos.org/plosone/art...l.pone.0082933