Original Articles

New DNA sequencing technologies are poised to trans-form the genetic evaluation of patients. Soon, the avail-ability of genetic information will no longer be a barrier to our understanding of the genetic basis of disease. Rather, our abil-ity to understand and interpret the data will be paramount. The interpretation of clinical genetic testing is a complex process that requires an appreciation of factors establishing causality as well as a detailed understanding of the tolerated genetic variation present in human genomes of different ethnicities. Until recently, much of the genetic variation in human popu-lations was unknown. With large-scale population sequenc-ing projects such as the 1000 Genomes Project,1 the true extent of this variation is now becoming clear. Indeed, recent analyses indicate a surprising prevalence of tolerated genetic variation.2–4 Editorial see p 59