Human genome
Sequencing

The first human genome sequences were published in nearly complete draft form in February 2001 by the Human Genome Project and Celera Corporation. Completion of the Human Genome Project's sequencing effort was announced in 2004 with the publication of a draft genome sequence, leaving just 341 gaps in the sequence, representing highly repetitive and other DNA that could not be sequenced with the technology available at the time. The human genome was the first of all vertebrates to be sequenced to such near-completion, and as of 2018, the diploid genomes of over a million individual humans had been determined using next-generation sequencing.

These data are used worldwide in biomedical science, anthropology, forensics and other branches of science. Such genomic studies have led to advances in the diagnosis and treatment of diseases, and to new insights in many fields of biology, including human evolution.

By 2018, the total number of genes had been raised to at least 46,831, plus another 2300 micro-RNA genes. A 2018 population survey found another 300 million bases of human genome that was not in the reference sequence. Prior to the acquisition of the full genome sequence, estimates of the number of human genes ranged from 50,000 to 140,000 (with occasional vagueness about whether these estimates included non-protein coding genes). As genome sequence quality and the methods for identifying protein-coding genes improved, the count of recognized protein-coding genes dropped to 19,000–20,000.

In 2022, the Telomere-to-Telomere (T2T) consortium reported the complete sequence of a human female genome, filling all the gaps in the X chromosome (2020) and the 22 autosomes (May 2021). The previously unsequenced parts contain immune response genes that help to adapt to and survive infections, as well as genes that are important for predicting drug response. The completed human genome sequence will also provide better understanding of human formation as an individual organism and how humans vary both between each other and other species.

Although the 'completion' of the human genome project was announced in 2001, there remained hundreds of gaps, with about 5–10% of the total sequence remaining undetermined. The missing genetic information was mostly in repetitive heterochromatic regions and near the centromeres and telomeres, but also some gene-encoding euchromatic regions. There remained 160 euchromatic gaps in 2015 when the sequences spanning another 50 formerly unsequenced regions were determined. Only in 2020 was the first truly complete telomere-to-telomere sequence of a human chromosome determined, namely of the X chromosome. The first complete telomere-to-telomere sequence of a human autosomal chromosome, chromosome 8, followed a year later. The complete human genome (without Y chromosome) was published in 2021, while with Y chromosome in January 2022.

In 2023, a draft human pangenome reference was published. It is based on 47 genomes from persons of varied ethnicity. Plans are underway for an improved reference capturing still more biodiversity from a still wider sample.
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