Yes, the UMIs are random 6 nt sequences that will be added to all samples. Therefore, the UMI sequence cannot be used to uniquely identify the different samples – only to tag distinct random priming events during library generation. The i7 (and i5) indices are added during library amplification and are
Learn more about UMIs, their function, and usage in our Lexicon Chapter #8.
The 12 nt Unique Dual Indexes (UDIs) are still required if multiple libraries need to be uniquely barcoded and pooled for sequencing in a single lane or run. The i7 and i5 index UDI sequences are added during the endpoint PCR and read-out during sequencing during with index reads 1 and 2, respectively, and are also . The index reads are required for sample demultiplexing after sequencing.
The i7 indices UDIs required for the final amplification of QuantSeq libraries are included as a bundle in every QuantSeq Library Prep Kit . In addition, 12 nt Unique Dual Indices (UDIs) can be added on to enable uniquely dual-indexed libraries for Illumina sequencing. QuantSeq Library Prep Kits and UDIs are available in bundle versions (Cat. No. 113 – 115, 129 – 131s 191 - 196).