One of the first things that became apparent in the study of complex disorders was that the practice of testing one or a few polymorphisms within a gene for association with a disease was at best insufficient. The number of known genetic variants increased exponentially making it clear that a gene can contain dozens or hundreds of single nucleotide polymorphisms (SNPs) that could influence its function. Although information on coding sequence and phylogenetic conservation information from the newly emerged field of comparative genomics could provide a means to assess the likelihood of function for any given SNP and reduce the number of tested SNPs, this is clearly an approach that could miss important variants.
