Human Genome Project
© 2013 Elsevier Inc. All rights reserved. The aim of the Human Genome Project (HGP) was to obtain the complete sequence of all the 3 billion (3×109) base pairs (bp) of DNA along the 24 human chromosomes. By 1986, the technologies of DNA cloning and sequencing had developed sufficiently to make sequencing a complete human genome a realistic possibility. However, it was not until the early 1990s that adequate funding was made available and the HGP actually started. The international HGP consortium chose to use mainly bacterial artificial chromosomes (BACs) for making maps of overlapping clones for very long DNA sequences, and then sequencing the BACs that formed the map. In 1998, a private venture launched an alternative 'shotgun' approach to sequence the human genome that involved omitting the BAC mapping phase and working directly only with sequences of relatively short clones. Both approaches required hundreds of automatic sequencers and considerable computer power. The first very preliminary whole-genome sequencing results were published in February 2001, a consensus preliminary complete sequence with 99.99% of sequences covered 10-fold published in 2004, and the polished final sequence finished with the publication of chromosome 1 in 2006. The whole effort was a remarkable achievement based on an international collaboration. A major conceptual outcome from the HGP was a more realistic estimate of the number of protein-coding genes, currently assumed to be around 19000. As the cost of DNA sequencing continues to plummet, there will be many individual whole-genome sequences produced. These DNA sequence data offer many opportunities for analyzing the patterns of human genetic variability and their relationship to disease and normal phenotypic variation, as well as the information the patterns can provide about human origins. There will also be continuing improvement in the understanding of the control language for complex patterns of differential gene expression during development and differentiation. There can be no doubt that the initial investment in the HGP has given an enormous return, both scientifically and financially.