Researchers of the Telomere-to-Telomere (T2T) consortium have completed a quest that started 32 years ago. They have uncovered the final DNA sequences that make up a human genome. They have published the first complete, gapless sequence of a human genome, two decades after the Human Genome Project produced the first draft human genome sequence.

The Human Genome Project that began in 1990 gave the first results of the complete human genome sequence in 2003. However, though it was announced as the complete human genome, about 15% of it was incomplete. Due to limitations of technology, scientists were not able to piece together some repetitive parts of the human genome. Solving some of the problems, an updated “complete” version was released in 2013, which still missed out on 8% of the genome. That last 8% includes numerous genes and repetitive DNA and is comparable in size to an entire chromosome.

Researchers of the Telomere-to-Telomere (T2T) consortium generated the complete genome sequence using a human cell line with only one copy of each chromosome. The researchers noted that most of the newly added DNA sequences were near the repetitive telomeres and centromeres.

Having a complete, gap-free sequence of the roughly 3 billion bases (or “letters”) in our DNA is critical for understanding the full spectrum of human genomic variation and for understanding the genetic contributions to certain diseases. The T2T consortium used the now-complete genome sequence as a reference to discover more than 2 million additional variants in the human genome. These studies provide more accurate information about the genomic variants within 622 medically relevant genes.

Quotation: “In the future, when someone has their genome sequenced, we will be able to identify all of the variants in their DNA and use that information to better guide their healthcare. Truly finishing the human genome sequence was like putting on a new pair of glasses. Now that we can clearly see everything, we are one step closer to understanding what it all means.”

Papers

Nurk et al. The complete sequence of a human genome. Science 376. Doi: 10.1126/science.abj6987 (2022)

Gershman et al. Epigenetic patterns in a complete human genome. Science 376. Doi: 10.1126/science.abj5089 (2022)

Vollger et al. Segmental duplications and their variation in a complete human genome. Science 376. Doi: 10.1126/science.abj6965 (2022)

Hoyt et al. From telomere to telomere: The transcriptional and epigenetic state of human repeat elements. Science 376. Doi: 10.1126/science.abk3112 (2022)

Aganezov et al. A complete reference genome improves analysis of human genetic variation. Science 376. Doi: 10.1126/science.abl3533 (2022)

Altemose et al. Complete genomic and epigenetic maps of human centromeres. Science 376. Doi: 10.1126/science.abl4178 (2022)

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