New Map for Gene Hunters
Midsize DNA variations could aid in search for disease genes

Results: Researchers led by Evan Eichler of the University of Washington have made a map of specific types of variation in the human genome, many of which had never been documented before: insertions, deletions, and inversions of pieces of DNA, the majority of which ranged from 8,000 to 40,000 letters long. By comparing the genomes of two people, they found 297 sites of such variations, including 139 insertions, 102 deletions, and 44 inversions. When they compared these sites to 16 that had been previously documented, they found that their map had identified seven of them, most of which were associated with disease risk or drug sensitivity. This suggests that more of these newly discovered variations may play a role in disease or drug response.

Why It Matters: To find disease-causing genes, researchers need maps showing the locations of genetic variations between individuals. In the last few years, researchers have been mapping single-nucleotide polymorphisms (SNPs), one-letter changes in the DNA sequence, both individually and in sets of thousands that occur together. Researchers have also identified much-larger-scale genomic differences between individuals but hadn't yet mapped intermediate-size variations such as insertions, deletions, and inversions. To do a comprehensive search for disease genes, researchers need to look at all types of variation. This new map can help them do that.