They intend to produce the first fully completed, highly accurate reference sequence of the human genome by the end of 2003, the year that marks the 50 th anniversary of the discovery of the structure of DNA by James Watson and Francis Crick. The rest of the human genome will be sequenced by the Sanger Centre in England, funded by the Wellcome-Trust, and through other sequencing centers around the world. The public genome project employs shotgun sequencing of DNA fragments that have been carefully mapped and stored. This process makes re-assembling the sequenced fragments to reflect their original position in the genome easier and more accurate, because the general location of the fragment in the genome is known. To return to the book analogy, it is much easier to re-assemble the text if all the fragments are known to come from a single page.
Scientists periodically encounter DNA fragments that are particularly difficult to sequence.
The international sequencing community, whose goal is to complete the human DNA sequence by the end of 2003, has agreed to a policy of releasing data every 24 hours into a free, publicly accessible database. DNA sequence derived by Human Genome Project laboratories is stored in databases scientists can freely access. Two efforts recently have been announced in the private sector to carry out human genome sequencing. These projects also employ a type of shotgun sequencing, but differ from the public effort in several significant ways. Because the scientist does not know where in the morass of 3 billion base pairs a particular fragment might belong, the task of re-assembling the fragments becomes far more difficult and prone to error.