What is it?
The Human Genome Project (HGP) is an international 13-year effort formally begun in October 1990. The project was planned to last 15 years, but rapid technological advances accelerated the completion to 2003. Project goals were to determine the complete sequence of the 3 billion DNA subunits (bases), identify all human genes, and make them accessible for further biological study. As part of the HGP, parallel sequencing was done for selected model organisms such as the bacterium E. coli to help develop the technology and interpret human gene function. The Department of Energy's Human Genome Program and the National Institutes of Health's National Human Genome Research Institute (NHGRI) together sponsored the U.S. Human Genome Project.

Goals of the project:
identify all the approximately 20,000-25,000 genes in human DNA,
determine the sequences of the 3 billion chemical base pairs that make up human DNA,
store this information in databases,
improve tools for data analysis,
transfer related technologies to the private sector, and
address the ethical, legal, and social issues (ELSI) that may arise from the project.

What happens now that the human genome sequence is completed?
The working draft DNA sequence and the more polished 2003 version represent an enormous achievement, akin in scientific importance, some say, to developing the periodic table of elements. And, as in most major scientific advances, much work remains to realize the full potential of the accomplishment.
Early explorations into the human genome, now joined by projects on the genomes of a number of other organisms, are generating data whose volume and complex analyses are unprecedented in biology. Genomic-scale technologies will be needed to study and compare entire genomes, sets of expressed RNAs or proteins, gene families from a large number of species, variation among individuals, and the classes of gene regulatory elements.
Deriving meaningful knowledge from DNA sequence will define biological research through the coming decades and require the expertise and creativity of teams of biologists, chemists, engineers, and computational scientists, among others. A sampling follows of some research challenges in genetics--what we still won't know, even with the full human sequence in hand.
Gene number, exact locations, and functions
Gene regulation
DNA sequence organization
Chromosomal structure and organization
Noncoding DNA types, amount, distribution, information content, and functions
Coordination of gene expression, protein synthesis, and post-translational events
Interaction of proteins in complex molecular machines
Predicted vs experimentally determined gene function
Evolutionary conservation among organisms
Protein conservation (structure and function)
Proteomes (total protein content and function) in organisms
Correlation of SNPs (single-base DNA variations among individuals) with health and disease
Disease-susceptibility prediction based on gene sequence variation
Genes involved in complex traits and multigene diseases
Complex systems biology including microbial consortia useful for environmental restoration
Developmental genetics, genomics