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Missing Variation

The Broad Institute's Daniel MacArthur has pulled together some 60,000 exomes from a range of sources to develop a library of genetic variation within humans, writes Ed Yong at the Atlantic.

At the Genome Science 2015 conference in the UK this week, MacArthur reported that his team uncovered some 10 million genetic variants within their library, many of which, Yong notes, had never before been described. Some of these variant only popped up once, indicating that they're only present in one out of every 60,000 people.

There were also variants the researchers expected to find, but didn't. A mathematical model developed by a postdoc on MacArthur's team successfully predicted neutral variants, but overestimated loss-of-function variants. This suggested to the researchers that these variants could be so harmful that people with them have severe disease or are never born. "The variants are simply not around to be sequenced because they have long been expunged from the gene pool," Yong says.

About a quarter of human genes, Yong says, fall into this category, and many of these haven't yet been linked to disease.

"We should soon be able to say, with high precision: If you have a mutation at this site, it will kill you," MacArthur says. "And we'll be able to say that without ever seeing a person with that mutation."