Announce that the complete sequence of the human genome has been obtained for the first time

An international team of scientists has announced that they have obtained for the first time the complete sequence of the human genome, including parts that were lost in the historic sequencing of the first human genome two decades ago.

This discovery – which has yet to be peer reviewed – would be beyond the realization of scientists from Human genome project (HGP), which in 2003, after an investment of nearly $ 3 billion in funding and thirteen years of careful research, announced that it had mapped the first sequence of the human genome.

American bioinformatician Adam Phillippy compares the situation so far in mapping the human genome with a puzzle of a landscape lacking the blue pieces of the sky, too similar to each other to be equipped with the technology of the time. A scientific team, called the T2T Consortium, has just published “the first sequence really complete“From a human genome.

Son 3.055 million nucleotides, the chemical letters with which a person’s instruction manual is written. The authors believe that the 8% of the genome was still unread.

The cell’s user manual, folded inside, is essentially a gigantic DNA molecule some meters length. There are guidelines so that, for example, a neuron in the brain knows how to transmit a thought. The cell’s instruction manual is written with combinations of only four chemical letters.

Current mass sequencing techniques – used in hospitals to study diseases with a genetic component – are unable to read the very long human genome, but they can recognize fragments hundreds of letters, which are then arranged using a reference genome, which acts as a photo of the landscape in the puzzle box.

The problem arises when putting together very repetitive stretches of DNA, as happens with the pieces of blue sky. To get around this obstacle, the researchers used advanced techniques, like the sequencers of the British company Oxford Nanopore, devices capable of reading hundreds of thousands of letters at the same time by passing them through a small pore.

Members of the T2T Consortium, led by biologist Karen Miga, of the University of California at Santa Cruz, and Adam Phillippy himself, of the National Institute for Human Genome Research, both in the United States, argue that “ a new era of genomics, in which no region of the genome is beyond reach ”.

The authors released a draft of their results on May 27. With their new data, the human genome would have 19,969 genes associated with protein production140 of them discovered by the consortium.

The members of the T2T Consortium propose to use their new sequence as global model. The current reference genome was developed in 2013, with DNA fragments from many people, by an international consortium in which the European Institute of Bioinformatics participates.

“The T2T consortium has completed the first truly complete sequence of 3.055 billion base pairs (bp) of a human genome, representing the greatest improvement of the reference human genome since its initial publication, ”the scientists wrote in an article published on the bioRxiv research server, which means that not yet peer reviewed.

The new genome is a Leap ForwardThe researchers said this was made possible by new DNA sequencing technologies being developed by two private sector companies: California-based Pacific Biosciences, also known as PacBio, and UK-based Oxford Nanopore. Its DNA reading technologies have very specific advantages over tools long considered essential by researchers.

“High-precision long-read sequencing ultimately removed this technological barrier, allowing in-depth studies of genomic variation throughout the human genome. Such studies will necessarily require a complete and precise reference human genome, which will ultimately lead to the adoption of the T2T-CHM13 set presented here, ”the researchers said in the article.

The genome the researchers sequenced it does not come from a person, but rather a hydatidiform mole, a rare lump or growth that forms inside the uterus at the start of pregnancy. This tissue is formed when the sperm fertilizes a nucleus-less egg, so it only contains 23 chromosomes, like a sperm or an egg, instead of the 46 found in the DNA of a human cell. These cells they simplify computational effort, but can be a limitation.

“We were just trying to explore this last incognito of the human genome,” Karen Miga, a researcher at the University of California, Santa Cruz, who co-led the international consortium told STAT News. “It’s never been done before and the reason it hasn’t been done before is because it’s difficult», He condemned.

The consortium explained that their work increased the number of DNA bases from 2.92 billion to 3.05 billion, an augmentation of 4.5%, and that the number of genes that code for proteins only increased by 0.4%, to 19,969. The researchers say the work could also lead to other new knowledge, including those related to how genes are regulated.

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