 Many of these alleles are (or have an increased likelihood of being) inherited together, meaning that they do not easily become separated through recombination events during  meiosis.[17]  This leads to the non-random association of different alleles at two or more loci, a phenomenon that has been dubbed ‘linkage disequilibrium’ or ‘LD’. The concept of LD is key for the HapMap project as the fact that some SNPs stay associated (whereas the clusters themselves might get separated from each other over time by recombination events) explains the haplotype structure of the genome (Daly et al. 2001). The term ‘haplotype’ simply refers to a particular cluster of alleles (in this case SNPs) that a) are on the same chromosomes and b) are commonly inherited as one. The aim of the HapMap project was to characterize human SNPs, their frequency in different populations and the correlations between them (HapMap 2003). The first haplotype map was published in 2005, reporting on data from 269 samples derived from four different populations (HapMap 2005). Five years later, a follow up was published, now reporting on data from 1184 individuals sampled from 11 different populations (HapMap 2010).