All of the glorious diversity that is the human race is derived, ultimately, from those two strands of material tightly wound around one another. But sometimes things go wrong. Many horrific diseases, like breast cancer, Huntington's disease and leukemia, are caused by genetic defects – "mistakes" somewhere in the 6 billion pairs of DNA chemical compounds. In this enormous, unique "database" we all possess, what is "normal" and what is a disease-causing mutation? To answer these questions, we need two things: a huge sample set of human DNA in a form that we can "sequence" (that is, enumerate each and every one of the six billion "base pairs") and massive amounts of computing and storage space to do our computations.