An international team of scientists, led by biologist Karen Miga, from the University of California at Santa Cruz, and Adam Phillippy, from the National Human Genome Research Institute, claims to have sequenced the entire human genomeor. In the draft published on May 27, the missing parts were included. in the first historical sequencing of the human genome 20 years ago, whose version had unfinished regions.
Background
In 2001, Celera Genomics and the International Human Genome Sequencing Consortium published their initial drafts of the human genome, that revolutionized the field of genomics. While these drafts and the updates that followed covered “the euchromatic fraction of the genome and the heterochromatin,” many other complex regions were left unfinished.
In 2003, after nearly $3 billion in funding and 13 years of painstaking research, scientists from the Human Genome Project (HGP) they claimed to have mapped the first sequence of the human genome.
complete genome
By addressing the remaining 8% of the unread genome, the Telomere-to-Telomere Consortium (T2T) finished the first truly complete sequence 3.055 billion base pairs (bp) of a human genome, representing the greatest progress in the task since its inception, the researchers explain in the publication BioRxiv. With the new data, the human genome would have 19,969 genes associated with protein production, 140 of them discovered by the consortium.
The new T2T-CHM13 reference includes gap-free sets for all 22 autosomes plus the X chromosome, corrects several errors, and introduces nearly 200 million bp of a new sequence containing 2,226 copies of paralogous genes, 115 of which are predicted to encode proteins . .
“The complete telomere-to-telomere assembly of a human genome will usher in a new era of genomics in which no region of the genome will be out of reach“said Karen Miga.
New technologies
This achievement was possible thanks to new DNA sequencing technologies developed by two private sector companies: the Californian Pacific Biosciences, also known as PacBio and the British Oxford Nanopore.
Its DNA reading technologies have very specific advantages over tools that have long been considered fundamental to researchers. “This 8% of the genome did not go unnoticed due to its relevance, but due to technological limitations”, wrote researchers Sergey Nurk, Arang Rhie and Mikko Rautianen.
“High-precision long read sequencing has finally removed this technological barrier, enabling comprehensive studies of genomic variation across the entire human genome. In any case, such studies necessarily require a complete and accurate human reference genome, which will ultimately drive the adoption of the T2T-CHM13 set presented here,” they added.
That is, current massive sequencing techniques are not able to read the very long human genome at once, but can recognize fragments of a few hundred letters, which are then ordered thanks to a reference genome, which acts as the photo of the landscape in the box puzzle.
What is a genome?
The genome is the set of genes contained in chromosomes, which can be interpreted as the totality of genetic material that an organism or a certain species has. In the case of the human genome, it is the DNA sequence contained in 23 pairs of chromosomes in the nucleus of each human diploid cell.
The DNA sequence that makes up the human genome contains the encoded information necessary for the expression of all human proteins. There are guidelines for, for example, a neuron in the brain to know how to transmit a thought.
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