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It looks like they're using Oxford nanopore and PacBio sequencing technologies for the long reads. These are two up-and-coming sequencing technologies focused on extremely long reads. My understanding of both is that their error rates on individual base pairs are too high to reliably determine the actual sequence on their own (something like 15% error rates). Typically the long reads from these technologies are used as a "scaffold" to resolve the large-scale structure of a DNA sequence, while another sequencing technology, usually Illumina, is used to resolve the actual sequence. (Illumina produces short reads, but it produces a lot of them, and the error rate is much lower, about 1%-5%.) In addition, since PacBio and Oxford Nanopore are very different technologies, I'm guessing that they probably have different "error profiles", so they probably partially cover for each others' deficiencies when you use both of them at the same time. Note: Don't take any of the specific numbers above as gospel. These technologies develop extremely quickly, so it's quite likely that my knowledge of typical error rates is out of date. In any case, here's the relevant quote from the original link (to phys.org), before it was changed to the less technical press release, which doesn't mention any specific technologies used: "The new project built on that effort, combining nanopore sequencing with other sequencing technologies from PacBio and Illumina, and optical maps from BioNano Genomics. Using these technologies, the team produced a whole-genome assembly that exceeds all prior human genome assemblies in terms of continuity, completeness, and accuracy, even surpassing the current human reference genome by some metrics." |