The task of finding the genetic roots of common disease seems a whole lot harder, dimming the promise of personal genomics and the chances of quick medical payoffs from the human genome project, given new data about the human genome in two reports published online in the journal Science on Thursday.
It now appears that large numbers of very rare genetic mutations may underlie common human diseases like schizophrenia and cancer. But because the mutations are so rare, costly studies involving large numbers of patients would be needed to identify their role in each disease.
Until recently, rare mutations have been hard to catalog because of the difficulty of distinguishing an unusual mutation from an error in the DNA decoding process. Now, however, a new generation of decoding machines allows each DNA unit in a genome to be examined 20 or more times, eliminating most errors.
The two reports in Science are particularly extensive surveys which establish that rare mutations are abundant in the human genome. Since most are likely to be deleterious, rare mutations could account for much of the burden of human disease, the authors say.