Last week marked a major milestone in studying the human genome. Since the early 2000s, the Human Genome Project has published successive versions of their map, or “sequence,” of the human genome. While rightfully acclaimed, even the final version was incomplete – leaving about 8% of the genome undeciphered -and the job not yet done. Subsequent work by the Genome Reference Consortium and others filled in only a portion of the gaps. Persistent technological limitations stymied these attempts, but those barriers have now fallen in what has been described as a technical tour de force, yielding close to a complete sequence.
The results are reported in a special April 1, 2022 issue of the journal Science, via six papers under the banner “Completing the Human Genome.” The Telomere-to-Telomere (T2T) Consortium achieved these results, succeeding in sequencing some 200 million additional base pairs – “steps” on the twisting ladder of the DNA double-helix comprising the genes that make up our twenty-three chromosomes – to approach 100% of the human genome. A far smaller fraction now remains problematic. In addition, after focusing on the X chromosome for publication, the T2T Consortium is said to have sequenced a Y chromosome as well. In short: this effort represents a new and improved reference sequence, or catalogue, for the human genome.
Such reference sequences can be vital in studying diversity across different human populations and groups. The DNA of any two humans is about 99.5% the same. Conversely, any genetic variation can prove consequential. Perhaps most intriguing, segments just mapped by T2T may play an important role in the replication, and evolution, of genes themselves. On a practical level this discovery should aid scientists in searching for genetic variations that lead to neurological and developmental disorders, for example, as well as for potential disease-inducing genetic variations. This, in turn, could ultimately transform both the day-to-day practice of medicine and how individuals come to regard their own healthcare choices.