An international group of scientists have completed the map of the human genome, the genetic blueprint of life, two years ahead of schedule.

In February 2001, two group of scientists revealed draft versions. This one fills in the gaps, covering 99 per cent of the gene-containing regions.

"After three billion years of evolution and several years of work by this coalition, we have before us the instruction set that carries each of us from the one-celled egg through adulthood to the grave," said Dr. Robert Waterston of the International Human Genome Sequencing Consortium.

"It is written in an arcane language and encompasses a complexity that we are just beginning to understand."

The consortium includes scientists from 18 institutions in the U.S., Britain, France, Germany, Japan and China who participated in the sequencing project. Their results are freely available to scientists and the computer database holding the sequence is receiving more than 120,000 visits a day.

Some areas of the sequence were harder to decipher because they are duplicated many times. The full sequence includes about three billion DNA letters, with fewer than one error per 10,000 letters.

Dr. Francis Collins, head of the National Human Genome Research Institute, said the next step is to apply the knowledge, which he says will touch biology, medicine and society.

The human genome contained between 35,000 and 40,000 genes, fewer than scientists expected. Proteins, the body's main building material for tissues, were more complex than thought.

Scientists still need to understand the structure and function of the genome, the interactions between genes and environmental influences, and differences across species.

Medical researchers are starting to apply their understanding of a disease's genetic cause to develop therapies, such as a new drug for a chronic form of leukemia.

But many of the advances in human genetics have been made for traits linked to a single gene, and most common diseases are more complex.

The complete genome was published in time for the 50th anniversary of the discovery of DNA's helical structure.