An organism's genome refers to all the hereditary information encoded in its genes. Sequencing a complete genome, a gene, or a fragment of genetic material involves determining the order of its sub-units: adenine, cytosine, guanine, and thymine.

Scientists are using individuals' genetic sequences to map and catalog human genetic variation in order to improve understanding of human biology, disease susceptibility, and drug response. As costs falls rapidly, the scale and speed of gene sequencing is increasing. The Human Genome Project required thirteen years and $3 billion to sequence the first complete, general human genome. Subsequent projects, such as the International HapMap Project, examined genetic variation between population groups, raising concerns of giving undue biological significance to social categories of race.

Now, the sequencing of complete genomes of specific individuals is becoming almost routine. For example, the Personal Genome Project plans to sequence 100,000 genomes.

Lower prices have also opened the door to companies that offer personal, direct-to-consumer genetic tests.