are some important exceptions. For example, the extensive LD surrounding the selected DRD4 7R allele [14] is not captured by these arrays, which contain very few SNPs in the region (only 1 in 100 kb). In general, however, the extensive long-range LD exhibited by these recently selected alleles (up to 1 Mb), and the current density of microarray SNPs, indicates that most of these evolutionarily important alleles can be “tagged” by an adjacent SNP surrogate.
