More than 10 years later, the 'grey zone' of the human genome is deciphered and its sequencing is completed

• Health "Genomic sequencing will help understand why Covid puts some people in the ICU"

21 years ago, the sequencing of the human genome was published

in two versions: one reached by the public consortium Human Genome Project (PGH) and another by the private company Celera Genomics.

In this way, facing the public, a

ended in a tie for being the first to decipher our

, each of the letters that make up a person's DNA.

Or so it seemed.

But there was more to know, because the sequences that were presented at that time, although they have represented an

in biomedical research, were

, since a not insignificant part of the DNA remained unknown.

Scientists like

were aware of this .

The investigator of the Howard Hughes Medical Institute (HHMI) of the University of Washington (Seattle), participated in the Human Genome Project.

The sequencing that culminated at the beginning of the 21st century was considered "complete" in the

that had

and were discarded as "garbage" because they had

.

But it was precisely in these "voids" that the regions in which Eichler was interested were found.

Therefore, he promised to finish the job one day: he had to read the entire genome, without skipping any paragraph.

Eicher's curiosity personalizes that of many other scientists, who wondered about this

DNA .

A few years ago, they planned to address that

sequencing

Pulling

and telecommuting during the pandemic, nearly a hundred researchers, many early in their careers, joined the

led by

of the National Human Genome Research Institute (Nhgri), and

, from the University of California at Santa Cruz (UCSC).

Today they present in the pages of

"chapters that have never been read before" from the genetic book of life.

From telomere to telomere, or from end to end of the chromosomes, they have assembled this new version, which they presented a few months ago, without peer review, on

.

Now, the scientific journal par excellence publishes in this week's number

with the conclusions of its research.

The reference version of the genome that is used today in laboratories around the world (GRCh38, which is part of the initial sequencing of the PGH) has millions of bases (nucleotides, the letters that follow each other in DNA)

, which means that

explains

geneticist

, who is not involved in the project , in

.

There are also regions of biological importance such as the

, the central part of the chromosomes, with highly repeated sequenced fragments that have not been assembled correctly.

All those still unknown parts account for about

.

The T2T consortium has deciphered them, thus adding 200 million nucleotides (something similar to the size of an entire chromosome) in

The fact that many protein-coding genes had not previously been found in these regions of DNA

to their ostracism.

But this trend for years is being reversed as its

for example, in gene expression and in certain diseases.

As one of the authors,

, of the MIND Institute at the University of California, Davis, points out, "These are

regions to sequence."

What is in the gray area not sequenced so far?

Genes have been found in the regions of that 8% and also unexpectedly high levels of

.

For co-director Phillippy, we are looking at "a

of variants that we can study to see if they have

."

The geneticist believes that "in the future, when someone's genome is sequenced, we will be able to identify all the variants in their DNA and use that information to

."

Co-director Karen Miga agrees with this, and is looking forward to "the

about these regions that have just been revealed."

The importance of the finding is also highlighted by the

(AEGH).

"For the first time, thanks to new technologies,

of the

DNA sequence can be reached," AEGH spokesman

told this medium .

The geneticist from the

(Ingemm) of the La Paz University Hospital (Madrid) explains that the sequencing has been possible thanks to "new generation technology that allows the completion

due to

". He also clarifies that the sequencing deciphers all the chromosomes, except for the Y, because it was not present in the cell line they have used. However, he concludes that it is "to date it is the genome with more detail and resolution published".

The new reference genome comes from a

derived from a type of tumor (hydatidiform mole) that appears when the egg loses its own genome in the uterus and is fertilized by sperm.

The scientists chose this type of cell to

, since it has two identical copies of each chromosome, unlike most human cells, which have two slightly different copies, from the father and from the mother.

Long reading, the key method to 'decipher' the gray area

The single-genome cell line "made assembly possible," says another of the authors,

, a neurogeneticist at Rockefeller University.

That, and technological advances.

Two "long -

have been used for sequencing

:

, which can read up to a million DNA letters in one go, albeit with modest accuracy, and

which reads about 20,000 .

lyrics almost perfectly.

As Jair Tenorio points out, compared to these

techniques , which allow very long fragments to be sequenced,

read

of about 1,000 letters.

"By being able to sequence very large fragments, the sequence is reliably resolved, especially in the centromeric or telomeric regions, where many repetitions are concentrated."

Applications of the new genomic sequencing

With the resolution of the

, sequences have been identified that could be related to protein synthesis, "so we could be, for example, facing

that potentially sequence

."

It will also be useful for studies of

and

, and to identify changes in these repetitive regions that may be associated with

.

A few years ago, Jair Tenorio, along with other researchers, identified a new syndrome - by the way, which has received the name of the geneticist - and of which new cases have recently been found.

The researcher speculates that the new reference genome may serve to resolve the unknown in

and which are linked to the resolved regions.

In fact, the human DNA version of T2T is already being used to re-analyze genomes collected by the

, an international project to create a catalog of human genetic variation.

Everything indicates that we will continue talking about the T2T consortium in the future, since its members affirm that they are already working to sequence a

inherited from father and mother.

They have also started a collaboration to obtain a

-genome , with complete DNA sequences from hundreds of people from all over the world, to obtain a more refined representation of

.

It seems that with the human genome, as with good books, something new is always discovered by rereading it.

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