For the first time, the complete sequence of the human genome has been deciphered.

An international consortium of scientists has published the first complete sequence and no gaps in a human genome, two decades after the Human Genome Project produced the first draft of the human genome sequence.

According to the researchers, having a complete sequence without gaps of the approximately 3 billion bases (or “letters”) of our DNA it is essential to understand the full spectrum of human genomic variation and to understand the genetic contributions to certain diseases.

Likewise, the sequence of the human genome, now complete, will be especially valuable for studies that seek to establish a global vision of human genomic variation, or differences in the DNA of people.

The work, published in the journal Science, was carried out by the Telomere to Telomere (T2T) consortium, led by researchers from the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health; the University of California Santa Cruz and the University of Washington (United States). The NHGRI was the main funder of the study.

These insights are vital to understanding genetic contributions to certain diseases and to using genome sequencing as a routine part of clinical care in the future.

Many research groups have already started using a pre-release version of the complete sequence of the human genome for their research.

8% remained to be mapped

The full sequencing builds on the work of the Human Genome Project, which mapped about 92% of the genome, and on research since then. Thousands of researchers have developed better laboratory tools, computational methods and strategic approaches to decipher the complex sequence. Six papers covering the full sequence have been published in ‘Science’, along with companion papers in several other journals.

The latest finding is in that last 8% that remained to be mapped and that includes numerous genes and repetitive DNA and its size is comparable to that of an entire chromosome. The researchers generated the complete genome sequence using a special cell line that has two identical copies of each chromosome, unlike most human cells, which carry two slightly different copies.

The researchers found that most of the newly added DNA sequences were found near the repetitive telomeres (the long, trailing ends of each chromosome) and the centromeres (dense sections in the center of each chromosome).

“Since the first draft of the human genome sequence was obtained, determining the exact sequence of complex genomic regions has been a challenge,” said Dr. Evan Eichler, a researcher at the University of Washington School of Medicine and co-chair. of the T2T consortium.

“I am delighted that we have achieved the work. The entire project is going to revolutionize the way we think about human genomic variation, disease and evolution,” he added.

Sequencing the human genome only costs a few hundred dollars

The cost of sequencing a human genome using “short read” technologies, which provide several hundred bases of DNA sequence at a time, is only a few hundred dollars, having dropped considerably since the end of the Human Genome Project. .

However, the use of these short read methods alone is still leaving some gaps in the assembled genomic sequences. Huge drop in DNA sequencing costs is accompanied by increased investment in new DNA sequencing technologies to generate longer DNA sequence reads without compromising accuracy.

In the last decade, two new DNA sequencing technologies have emerged that produce much longer sequence reads. The Oxford Nanopore DNA sequencing method can read up to a million DNA letters in a single read with modest accuracy, while the PacBio HiFi DNA sequencing method can read about 20,000 letters with almost perfect precision.

“One step closer to understanding what it all means”

Researchers in the T2T consortium have used both methods of DNA sequencing to generate the complete sequence of the human genome.

“Thanks to long reading methods, we have made advances in our understanding of the most difficult and rich parts in repeats of the human genome”, explained Dr. Karen Miga, co-chair of the T2T consortium, whose research group at the University of California, Santa Cruz, is funded by the NHGRI.

“This complete sequence of the human genome has already provided new insights into genome biology, and I look forward to the next decade of discoveries about these newly revealed regions,” Miga said.

According to consortium co-chair Dr. Adam Phillippy, whose research group at NHGRI has led the project, he believes sequencing a person’s entire genome should become less expensive and easier in the coming years. “In the future, when a person’s genome is sequenced, we will be able to identify all the variants in their DNA and use that information to better target their healthcare.”

“Really finishing the sequence of the human genome has been like putting on new glasses. Now that we can see everything clearly, we are one step closer to understanding what it all means,” it is finished.

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George Holan

George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.

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