A new look at the human genome suggests that unappreciated variations in its fundamental architecture, rather than point-by-point mutations, may be responsible for most genetic difference among people.
Point-by-point mutations, called single nucleotide polymorphisms, involve simple changes to DNA lettering. They’re the best-studied type of variation, the target of most genomic disease hunts, and the substance [...]
Source: http://www.wired.com/wiredscience/2011/07/genome-structure/