April 14, 2003

Human Genome Project

International consortium announces completion of the Human Genome Project

The project declared itself finished with fewer than 400 stubborn gaps still open — down from about 150,000 in the working draft three years earlier.

14 April 2003: two years early

On 14 April 2003, the International Human Genome Sequencing Consortium announced that the Human Genome Project's high-throughput sequencing phase was complete — more than two years ahead of its original 2005 target. The U.S. effort, co-led by the National Human Genome Research Institute under Francis Collins and the Department of Energy, had cost about $2.7 billion in fiscal-1991 dollars.

What researchers received was a finished reference containing about 99 percent of the gene-containing — euchromatic — human sequence, at an announced accuracy of 99.99 percent.

Reading the famous 99% correctly

The headline number needs its denominator. The claim was 99 percent of the *euchromatic* portion — not of every base in the genome. The later observation that the reference omitted roughly 8 percent of the total genome does not contradict it; the two percentages measure different things.

'Completed' was likewise an operational milestone, not a claim that every telomere, centromere and heterochromatic repeat had been read. The remaining euchromatic holes were concentrated in fewer than 400 defined gaps whose structures the technology of the day could not reliably sequence.

The end of a program, not of the work

The announcement ended the coordinated, industrial-scale sequencing program that had formally begun in 1990, with public centers in the United States, United Kingdom, France, Germany, Japan and China contributing under the rapid-release Bermuda Principles.

The sequence itself was a composite reference from multiple donors — not one person's genome — and the consortium's peer-reviewed finishing paper followed separately in October 2004. The Telomere-to-Telomere Consortium published a far more complete reference in 2022; the first complete, gapless Y-chromosome sequence followed in 2023.

Sources

Researched 23 Aug 2026 7 sources 3 audit passes, 1 issue open

How this was checked

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What the sources leave uncertain

The headline formulation '99% of the human genome' is too broad. The contemporary claim was approximately 99% of the gene-containing or euchromatic portion, at 99.99% accuracy.
The later 2004 peer-reviewed assessment estimated roughly one error per 100,000 bases—99.999%—and reported 341 gaps. Those refined figures should not be substituted silently for the numbers announced on April 14, 2003.