genomes (such as the 1000 Genomes Project) is already underway. The International HapMap Project, which was also established in 2003, identifies and catalogs all common human genetic variants with the goal of using this information to find the genes that affect health, diseases, and individual responses to medications and environmental factors. To date, some 22 million polymorphisms are known and the allele frequencies and linkage disequilibrium relationships of many have been defined in HapMap which has a set of four world populations, and in the Human Genome Diversity Panel, a collection of 51 smaller population samples worldwide. However, despite efforts such as the ENCODE Project, our ability to identify variations in the human genome has vastly exceeded our understanding of their biological significance, a problem that is particularly important in unraveling the basis of common disorders such as drug addictions.
