Although GWA discovery studies provide valuable clues to genomic function and pathophys-iologic mechanisms, they are only a first step in identification of disease genes and are many steps removed from actual clinical application. Nonetheless, they tend to receive considerable media attention and have the potential for generating queries from patients about whether to get tested for the “new gene for Disease X” based on the latest report (50). As noted above, many SNPs identified from such studies, as well as the genes or regions containing them, are currently of unknown function.Inad-dition, SNPs from GWA studies in complex diseases (unlike many Mendelian disorders) do not predict unequivocally who will develop disease and who will remain free of it. Instead, individuals carrying a particular risk genotype implicated in a GWA study have a greater risk (and sometimes only a modestly greater risk) of developing a complex disease than those who do not.
