It is expected that functional variants discovered through resequencing of regions implicated by tag SNPs will uncover larger genetic effects [95]. Another conjecture that is finding increasing support is that rare rather than common variants, or a combination of both, might account for the unexplained variability of complex traits [105]. This conjecture could reinvigorate interest in family based studies, which are more powerful to detect rare variants with high penetrance [50]. Because most of the rare variants are probably unknown and the SNP arrays that are available are mainly designed to capture common variants catalogued through the HapMap project, only further SNP discovery through fine mapping and deep sequencing will unveil the truth [106].
