What differentiates people from each other, genomically speaking? Is it our SNPs, our CNVs, our rearrangements? A new study published in Nature Biotechnology suggests that it's really "unappreciated variations in [the genome's] fundamental architecture," rather than single point-by-point mutations that really make up the differences between people, reports Wired's Brandon Keim. While SNPs are the most common variations and the most widely studied for their associations with disease, large-scale changes like duplications and reversals, or additions or omissions of long DNA sequences, are less studied, Keim says. The study's authors say that these longer sequences are more specific to individual people than SNPs are, and suggest that traditional genome sequencing techniques are too focused on short reads to show the whole picture. "It might seem counterintuitive that big changes have been harder to detect than small ones, but it’s a consequence of how genomes are read," Keim says. "Every method involves breaking long DNA sequences — the human genome contains three billion DNA pairs — into pieces, then trying to reassemble them. The methods vary according to fragment size and reassembly technique, but as a rule it’s far less expensive and time-intensive to use small fragments." But like a jigsaw puzzle, it would be easier to put the picture together if we were using larger pieces, he adds.
Aug 05, 2011