The Human Genome Project involved laboratories in the United States, France, Great Britain, Germany, and Japan. It was financed in the United States by the National Institutes of Health and by the Department of Energy and in Great Britain by the Wellcome Trust of London. A comparable project using new DNA (genetic material) sequencing machines was begun as a private industry venture in the United States in 1998, with a stated goal of completing the mapping of the genome in three years.

Early in 2001 scientists from both teams jointly announced the completion of the mapping of the human genome, indicating that they had identified an estimated 30,000 genes (instead of the expected 100,000), constituting just 1% of the total human DNA. Subsequent comparison of the two teams' data has indicated that, because of differences in the genes identified by the teams, there may in fact be as many as 40,000 human genes. A subsequent, more refined estimate (2004) based on additional work on the genome was that there are between 20,000 and 25,000 genes. Work continues on further refining the sequencing of the genes on the chromosomes, eliminating the remaining gaps in the genome map, and identifying the extent of variation in the human genome. In 2007 the first sequences of human individuals (James D. Watson and J. Craig Venter, who led the public and private human genome sequencing efforts, respectively) were released. The NIH's National Center for Biotechnology Information maintains GenBank, a database of publicly available genetic sequences from the genomes of plants and animals, including some extinct species.