With the completion of a canonical sequence for the human genome in 2003, and very rapid advances in DNA sequencing technologies, the possibility that sequencing of all three billion DNA base pairs will become routine in medical practice is not farfetched. The canonical human genome sequence was a 13-year effort involving DNA fragment cloning, shotgun sequencing of random DNA fragments, advances in bioinformatic capabilities for sequence assembly, and required the efforts of hundreds of people and machines at a cost of $3 billion dollars. Using sequencing technologies in which up to a billion DNA fragments are simultaneously sequenced in a single run on one machine, a human genome can now be sequenced in several weeks for less than $50,000 (8). The $1,000 genome is thought to be a reasonable goal within the next few years, and large-scale sequencing of human 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
