Genetic variation catalog expanded

On Wednesday, researchers reported the latest results from the 1000 Genomes Project,__ a large international colla...
On Wednesday, researchers reported the latest results from the 1000 Genomes Project,__ a large international collaboration that seeks to map out human genetic variation, in the journal Nature.

Sequencing DNA from 1,092 people from 14 populations (including Europeans, East Asians, Sub-Saharan Africans and people from the Americas) they identified 38 million DNA variants in the genome _ the collection of 6 billion DNA letters that form the biological blueprint for a person.

Having such a _dense catalog_ of DNA variants should help researchers figure out what genetic variations correlate with disease, said Carlos Bustamante, a geneticist at Stanford Medical School and a participant in the project.__ In the future, when researchers sequence the genome of a person with, say, diabetes, they_ll be able to compare the variations they find in that subject_s DNA to the 1000 Genomes reference genomes to do a sort of _first-level check_ _ to begin to figure out if a particular genetic difference is or isn't the cause of the disease.

_You can now ask, has anyone seen this mutation before?_ Bustamante said, adding that _if a variation is common, it_s unlikely that it underlies_ a rare disease trait.

A pilot phase of the project, which looked at DNA from several hundred people, revealed more than 95% of common variants that appear with more than 5% frequency in people, the team reported in the new Nature paper.__ (For more on the initial 1000 Genomes results, check out this story by former L.A. Times writer Thomas Maugh II.) But important, lower-frequency genetic differences that may not have shown up in the smaller study account for the majority of differences among humans, Bustamante said.

One fascinating detail in the new research: patterns observed in the distribution of these lower-frequency variants reflected events in human history.__ For example, the new data showed that these rare variants, which are relatively new, tended to cluster in populations--suggesting that as populations have boomed in the last 10,000 years, novel mutations haven_t yet had time to spread widely.

Because of this localization of variation, in the future researchers will need to sequence genomes from a broad array of populations to make sure they catch rare and potentially disease-causing variants, Bustamante said.

That next phase of 1000 Genomes data-crunching is already underway, he added.

By Eryn Brown

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