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The sequence will be especially valuable for studies that aim to establish a global view of human genomic variation, or differences in people's DNA.
An international consortium of scientists has published the first complete, gap-free sequence of a human genome, two decades after the Human Genome Project produced the first draft of the human genome sequence.
According to researchers, having a complete, gap-free sequence of the approximately 3.000 billion bases (or "letters") of our DNA is fundamental to understanding the full spectrum of human genomic variationand to understand the genetic contributions to certain diseases.
The T2T consortium used the now complete genome sequence as a reference to discover more than 2 million additional variants in the human genome. These studies provide more precise information on genomic variants within 622 medically important genes.
"The generation of a truly complete human genome sequence represents an incredible scientific achievement, providing the first complete view of our DNA," explains Dr. Eric Green, director of the NHGRI. "This fundamental information will reinforce the many ongoing efforts to understand all the functional nuances of the human genome, which in turn will enhance genetic studies of human diseases".
The now complete human genome sequence will be especially valuable for studies aimed at establish a global view of human genomic variation, or differences in people's DNA.
This knowledge is vital to understand the genetic contributions to certain diseases and to use genome sequencing as a routine part of clinical care in the future. Many research groups have already started using a pre-publication version of the complete human genome sequence for their research.
The complete sequencing is based on the work of the Human Genome Project, which mapped about 92% of the genome, and on research carried out since then. Thousands of researchers have developed better laboratory tools, computational methods and strategic approaches to decipher the complex sequence. Six articles covering the entire sequence are published in 'Science', along with complementary articles in several other journals.
That last 8% includes numerous genes and repetitive DNA and is comparable in size 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 observed that most of the new DNA sequences added were near the repetitive telomeres (long, trailing ends of each chromosome) and centromeres (dense sections of 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'm delighted that we got the job. The entire project is going to revolutionize the way we think about human genomic variation, disease and evolution".
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 decreased considerably since the end of the Human Genome Project.
However, Using these short read methods alone still leaves some gaps in the assembled genomic sequences. The huge decline in DNA sequencing costs is accompanied by increased investments 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 letters of DNA in a single read with modest accuracy, while the PacBio HiFi DNA sequencing method can read about 20.000 letters with near-perfect accuracy. Researchers in the T2T consortium used both DNA sequencing methods to generate the complete human genome sequence.
"Thanks to long read methods, we have made progress in our understanding of the most difficult and repetition-rich parts of the human genome," says Dr. Karen Miga, co-chair of the T2T consortium, whose research group at the University of California, Santa Cruz, is funded by 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.".
According to consortium co-chair Dr. Adam Phillippy, whose research group at NHGRI led the finishing effort, Sequencing a person's entire genome should be 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 guide your healthcare -Phillippy points out-. Actually 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."
Source: Heraldo de Aragón
