Genetic variants are often inherited together in segments of DNA called haplotypes. These ancestral genomic segments are inherited as discrete units with little genetic shuffling across generations. Because haplotypes are shared by a majority of the human population, they can be used to decipher the genetic differences that make some people more susceptible to disease than others. Today, an international consortium coordinated by the National Institutes of Health works to map the pattern of common haplotypes throughout the genome. The Haplotype Mapping (HapMap) group at the Broad Institute plays a key role in this global effort by generating new data and creating novel analytic methods to study haplotype information.
The sequence variants in a haplotype are called single nucleotide polymorphisms, or SNPs. In many cases, the SNPs in a given haplotype are redundant, such that only a few are needed to characterize the genetic diversity of the entire block. The HapMap project's chief goal is to identify sets of representative SNPs, or tags, that provide this predictive capacity. As the number of identified tags grows, the number of SNPs required to study the genome decreases. In consequence, efforts to identify risk genes for disease proceed in a more timely and cost-effective manner.
The group's activities are divided into two key phases. The first generates SNP data using high-throughput analytical tools. The second phase is devoted to data analysis and efficient tag selection. The resultant HapMap, often referred to as the next-generation map of the human genome, will be used to identify risk genes that affect health, disease, and drug responses.