The potential of using these abundant SNPs in association studies motivated a large-scale international cataloguing effort, the SNP Consortium 5. The database used for submission, dbSNP, currently holds >10 million SNPs. Conducting association studies by genotyping samples for all known polymorphisms is not financially feasible nor necessary: various studies showed that alleles of SNPs located close together on a chromosome are not inherited independently within a population, but are correlated, such that many individuals share the same haplotype (haplotype blocks) 6. This correlation between genetic variants within a population is termed ‘linkage disequilibrium’ (LD), and it is this feature that is utilised in marker selection.
