Nature reports a complete sequence of the human chromosome for the first time at an unprecedented level of accuracy. The report shows a telomere-to-telomere (end-to-end) assembly of a human X chromosome, which fills up the gaps and supplements the current reference genome known as Genome Reference Consortium build 38 (GRCh38).

The research team achieved this breakthrough by high-coverage, ultra-long-read nanopore sequencing of the complete hydatidiform mole CHM13 genome, together with complementary technologies for quality improvement and validation. They focused on the human X chromosome and constructed the ~3.1 megabase centromeric satellite DNA array and closed all 29 remaining gaps in the current reference, including a new sequence from the human pseudoautosomal regions and cancer-testis ampliconic gene families.
With the complete sequence of the human chromosome, the researchers are confident that completing the human genome sequence is achievable.
[www.nature.com]