Human Genome Map Is Completed

"Scientists have unveiled what they call the first complete map of a human genome, filling in significant gaps that persisted for almost 20 years and setting the stage for new discoveries about human evolution and fresh insights into cancer, birth defects and aging.

The newly mapped regions, described in six papers published this week in the journal Science, include parts of the genome that had long been uncharacterized because of the limits of DNA-sequencing technology.

"This is the first gapless sequence of a human genome," Dr. Eric Green, director of the National Human Genome Research Institute, said Thursday at a press event about the new map. The institute, part of the National Institutes of Health, was a major funder of the project.

The scientists behind the research identified 99 new genes that likely code for proteins essential to human life, along with 2,000 more whose function is unclear.

Exploiting the new map for medical care would likely take years of additional research, said Dr. Wendy Chung, a Columbia University geneticist who wasn't involved in the effort. But the map "gets us to the starting line," she said, adding, "We have patients with diseases that we know are genetic but we haven't been able to identify. I hope this map will help us fill in some of the gaps in our knowledge."

The scientists also corrected thousands of errors in an earlier map of human DNA, which has served as a reference for doctors, geneticists and researchers since its completion in 2003. That landmark effort, the result of the $3 billion Human Genome Project, sought to read every letter of a person's DNA but even with refinements made in the ensuing years is believed to have found only about 92% of them.

The researchers behind the new map were determined to find the missing 8%.

"Many of us did not want to walk away. We wanted to finish the genome," said University of Washington geneticist Evan Eichler, who participated in the Human Genome Project and is now a member of the Telomere-to-Telomere Consortium.

The consortium, named for the caps at the tips of chromosomes to indicate that the chromosomes would be sequenced in their entirety, is a grass-roots effort involving more than 100 scientists from around the world.

The new map cost a few million dollars to create, according to Adam Phillippy, a computational biologist at the National Human Genome Research Institute, reflecting how sequencing costs have fallen sharply over the years.

The twin strands of DNA in human cells contain about three billion letter pairs spread among 23 pairs of chromosomes. The genetic material helps determine eye and hair color, stature and other physical characteristics, as well as risks for certain diseases.

Sequencing machines can't read all those letters at the same time. Instead, the machines read segments, typically ranging from a few hundred to a few thousand letters. Once the individual segments are sequenced, computers are used to determine the order of the segments and thus the overall map of the genome.

Scientists liken the process to assembling a giant jigsaw puzzle. Human cells typically contain two genomes, one from the mother and one from the father.

"It is like having two identical puzzles that only vary slightly in the same box," said Karen Miga, an assistant professor of biomolecular engineering at the University of California, Santa Cruz, who helped organize the consortium.

Consortium scientists said they hoped the technique used to create the new map would fuel other continuing projects, including a "human pan-genome reference" based on DNA from hundreds of individuals of different ancestries to better reflect the world's genetic diversity. The field of genetics has struggled for years with a lack of diversity in DNA databases, Dr. Eichler said.” [1]

1.   U.S. News: Human Genome Map Is Completed
Marcus, Amy Dockser.
Wall Street Journal, Eastern edition; New York, N.Y. [New York, N.Y]. 01 Apr 2022: A.3.