Researchers release complete mapping of human genome

Researchers working with the National Human Genome Research Institute have been able to map a complete human genome for the first time, Photo courtesy of the National Human Genome Research Institute
1 of 5 | Researchers working with the National Human Genome Research Institute have been able to map a complete human genome for the first time, Photo courtesy of the National Human Genome Research Institute

NEW YORK, March 31 (UPI) -- An international team of researchers on Thursday released the first complete sequence of a human genome, which will increase understanding of genetic variations and mutations that contribute to diseases, such as cancer, and help find cures, the scientists said.

The full, gap-free sequence of the roughly 3 billion bases, or "letters," in human DNA was completed nearly 20 years after the Human Genome Project produced its "first draft." The new achievement was reported in a series of articles published by Science.


Filling in pre-existing gaps in DNA also could provide clues about how certain genetic conditions, including mental health disorders that range from autism to schizophrenia, and certain personality traits, develop.

"This is a remarkable achievement, [and] it has given us at long last a complete view of human DNA," Dr. Eric Green, director of the National Human Genome Research Institute, said during a press conference Thursday.


The first, fully sequenced genome, of a human of European ancestry, will provide future researchers with a template, or "reference," to guide future research, Green and his colleagues at the institute said.

"In the short term, a complete genome improves mapping and discovery of genetic variation across the entire human genome, [so] we will have increased power to make associations with human traits, both disease and otherwise," one of the researchers involved, Evan E. Eichler, told UPI in an email.

"In addition, a complete genome provides access to regions and genes that were previously intractable, we now have a path to characterize this variation more systematically," said Eichler, a Howard Hughes Medical Institute investigator at the University of Washington in Seattle.

The first draft of the human genome, first released in 2003 by the Human Genome Project, actually mapped about 92%, according to the National Human Genome Research Institute, which is overseeing the work.

The remaining 8%, which accounts for roughly 2,000 previously missing genomic regions and is part of the complete genome released Thursday, includes 2 million additional genetic variants within 622 medically relevant genes, the researchers said.

Using the online messaging platform Slack to communicate, researchers from 30 different institutions worldwide added or corrected more than 200 million DNA base pairs, or two chemical bases bonded to one another to form a "rung" of the DNA ladder.


This increased the total number of DNA base pairs in the human genome to 3.05 billion and identified 100 new genes capable of producing proteins, which are essential to many functions and processes in the human body, the researchers said.

The entire genome is made of four types of DNA base pairs, which, in groups of three, code for the amino acids used to build proteins, they said.

"The addition of nearly 200 million base pairs of sequence --- on the scale of an entire new chromosome -- to the reference genome allows for the discovery of new genetic variations, including those that cause disease," another of the project researchers, Rajiv McCoy, told UPI in an email.

"It is very likely that we will identify novel disease associations that were hidden within these technically challenging regions," said McCoy, an assistant professor of biology at Johns Hopkins University in Baltimore.

In an aspect of the research led by McCoy and his team, the availability of a complete human reference genome was found to "greatly improve" the accuracy of structural variant identification, or "large-scale genome rearrangements and gains and losses of portions of chromosomes," he said.

This was based on an analysis that compared the reference genome with genetic data collected from more than 3,200 people from around the world, McCoy and his colleagues said.


In the past, structural variation has been "technically very challenging to study" due to limitations in DNA sequencing technologies, according to McCoy.

However, the latest generation of long-read DNA sequencing technologies, which have also helped make the process less expensive, "have revolutionized our ability to discover these mutations and their impacts on human health," McCoy said.

"This could indeed be a game-changer for the genomic study of cancer, developmental disorders and other diseases to which these variants contribute," he said.

Although, the complete genome "improves our understanding of genetics in principle of all diseases," the new genes and parts of genes that are being uncovered have a wide range of functions, Eichler added.

This includes genes important in aging, brain function, immunity, heart disease and drug detoxification, he said.

In addition, the new findings provide more insight into a previously poorly understood component of the genome called centromeres, or dense bundles of DNA that hold chromosomes together and play a key role in cell division, according to the researchers.

Historically, centromeres had been considered unmappable because they contain thousands of stretches of DNA sequences that repeat multiple times, they said.

Being able to track changes to centromeres over time will allow researchers to make more precise between generations or people of different racial and ethnic origins, the researchers said.


The DNA sequences in and around the centromeres make up about 6% of the entire genome, or nearly 190 million DNA base pairs, according to the researchers.

Of the remaining newly added sequences, most are found around the telomeres at the end of each chromosome and in the regions surrounding ribosomal genes, they said.

This could provide additional clues to the changes behind "any complex genetic disorder where we have an incomplete understanding of the genes that cause them, such as autism, schizophrenia or cancer," Megan Dennis, another of the researchers involved, told UPI in an email.

These clues "may exist within these newly ... discovered regions," said Dennis, an assistant professor of biochemistry and molecular medicine at the University of California, Davis School of Medicine.

Mapping the remaining 8% took nearly two decades, or nearly twice as long as it took to sketch the original 92%, the National Human Genome Research Institute's Green said Thursday.

However, it was also done at a "fraction" of the cost thanks to recent advances in genetic analysis technology, Adam Phillippy, a senior investigator at the National Human Genome Research Institute, said during Thursday's press conference.

As understanding of the genome grows and testing technology improves, the costs for genetic evaluations for patients could soon fall below $1,000, allowing "precision medicine," or health management based on genetic risk factors, to "become routine," he said.


This is likely still years away, according to the University of Washington's Eichler.

"Today's announcement is not the end but the beginning," Eichler said. "The best is yet to come in terms of the impact on the study of genetics [and] on clinical medicine."

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