A large international team of researchers is claiming to have at last
sequenced the entire human genome. Collectively, the team is known as the
Telomere-to-Telomere (T2T) Consortium, and they have written a paper
describing their efforts and have uploaded it to the bioRxiv preprint
server.
Back in 2000, a team from the Human Genome Project working with biotech firm
Celera Genomics announced that they had completed the first draft of a
sequencing of the human genome. That first draft was missing approximately
15% of the genome. Work since that time has brought the percentage down to
just 8%. And now, the T2T Consortium is claiming to have reduced it to
zero—though there are still some caveats. The group acknowledges that they
had some trouble with approximately 0.3% of the genome, and there might be a
few errors here and there—but no gaps, which is why the group have called
themselves the Telomere-to-Telomere Consortium. As part of their work, the
team discovered approximately 115 new genes that code for proteins, giving a
new total of 19,969.
The researchers suggest their work was only possible because they had use of
new technology developed by Oxford Nanopore and Pacific Biosciences—the new
technology allowed for sequencing without cutting the DNA into pieces. It
instead ran the DNA through a nanoscopic hole with lasers reading the
sequences repeatedly to reduce errors. They also claim that the number of
known bases has now grown from 2.92 billion to 3.05 billion and the number
of known genes has increased by 0.4%.
The researchers also note that the genome they sequenced did not come from a
person but rather a hydatidiform, which is a growth that on rare occasions
forms on the inside of a woman's uterus. Such growths occur when a sperm
manages to fertilize an egg that has no nucleus; thus, it has just 23
chromosomes rather than the normal 46 found in most human cells. The
researchers chose to sequence the hydatidiform because it made their
computations easier.
The results have yet to be peer reviewed, which is why the genomics
community is holding off on commenting—in the meantime, the T2T team is
making plans to take their work further by sequencing multiple people from
across the globe.
Reference:
Sergey Nurk et al, The complete sequence of a human genome, bioRxiv (2021).
DOI:
10.1101/2021.05.26.445798