Which orientation should the index sequences have? (barcode sequences)

Demultiplexing service is included by default for all sequencing run types for standard barcodes. If you would like us to demultiplex, please provide barcodes in the libraries table in the COREOMICS submission system.
Unfortunately, we cannot demultiplex inline barcodes.
Required Orientation of Index Sequences:
Depending on sequencer model, the second index (called i5 index) will be read in different orientations. The correct adapter sequence information for the sample sheets is usually provided for both options by kit manufacturers. The two sequences are reverse complements of each other.

  • The Forward Strand Workflow (previously known as Workflow A) sequences are required for MiSeq and AVITI.
  • The Reverse Strand Workflow (previously Workflow B) sequences are required for NovaSeqs and NextSeq.

BTW, the AVITI demultiplexing software is smarter and can figure out the correct orientation on its own. Either orientation will be fine for AVITI submissions.

Here is the complete information on this topic from Illumina:  https://support-docs.illumina.com/SHARE/IndexedSeq/indexed-sequencing.pdf


Category: 03 Sample Preparation & Sample Requirements, 05 Sequencing

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