Fifty years after the discovery of the double helix structure of DNA, the genome community is celebrating the elucidation of the human DNA reference sequence. Sequence data are available for downloading now. Annotation of genes and other genomic features is still under development and will be available for browsing when complete.

Reference Sequence Properties

Chrom. number	Reference accession	Sequence length	Determined bases*
1	NC_000001.4	245,203,898	218,712,898
2	NC_000002.5	243,315,028	237,043,673
3	NC_000003.5	199,411,731	193,607,218
4	NC_000004.5	191,610,523	186,580,523
5	NC_000005.4	180,967,295	177,524,972
6	NC_000006.5	170,740,541	166,880,540
7	NC_000007.7	158,431,299	154,546,299
8	NC_000008.5	145,908,738	141,694,337
9	NC_000009.5	134,505,819	115,187,714
10	NC_000010.4	135,480,874	130,710,865
11	NC_000011.4	134,978,784	130,709,420
12	NC_000012.5	133,464,434	129,328,332
13	NC_000013.5	114,151,656	95,511,656
14	NC_000014.4	105,311,216	87,191,216
15	NC_000015.4	100,114,055	81,117,055
16	NC_000016.4	89,995,999	79,890,791
17	NC_000017.5	81,691,216	77,480,855
18	NC_000018.4	77,753,510	74,534,531
19	NC_000019.5	63,790,860	55,780,860
20	NC_000020.5	63,644,868	59,424,990
21	NC_000021.3	46,976,537	33,924,742
22	NC_000022.4	49,476,972	34,352,051
X	NC_000023.4	152,634,166	147,686,664
Y	NC_000024.3	50,961,097	22,761,097
unplaced	various	25,263,157	25,062,835
* HGP goals called for determination of only the euchromatic portion of the genome. Telomeres, centromeres, and other heterochromatic regions have been left undetermined, as have a small number of unclonable gaps.

Sequence data production was handled by several genome centers in the U.S., the U.K., Japan, France, and China. Bioinformatics support on the coordination and evaluation of the data was provided by the National Center for Biotechnology Information (NCBI), the University of California at Santa Cruz (UCSC), and Project Ensembl in the U.K. The human reference sequence represents one of the most significant contributions to RefSeq, the NCBI's database of reference sequences of genomes, mRNAs, and proteins from all branches of the Tree of Life.

Assembly and annotation runs are often referred to by "build numbers". This reference sequence is build 33. The current genome release available for browsing in the NCBI Map Viewer is build 32, in which several of the chromosomes had been finished, but others still contained draft sequence data. The annotation process typically takes about 3 weeks and build 33 annotation will appear in the Map Viewer as soon as it is available. Genome Browsers at UCSC and Ensembl have independent annotation pipelines and may make annotation available earlier.

Further Reading Finished Chromosomes Dunham, I. et al. (1999). The DNA sequence of human chromosome 22. Nature 402, 489-495. Hatorri, M., et al. (2000). The DNA sequence of human chromosome 21. Nature 405, 311-319. Deloukas, P., et al. (2001). The DNA sequence and comparative analysis of human chromosome 20. Nature 414, 865-871. Heilig, R., et al. (2003). The DNA sequence and comparative analysis of human chromosome 14. Nature, epub ahead of print. Working Draft Sequence The International Human Genome Sequencing Consortium (2001). Initial sequencing and analysis of the human genome. Nature 409, 860-921. The International Human Genome Mapping Consortium (2001). A physical map of the human genome. Nature 409, 934-941. Using the Working Draft Jang, W., et al. (1999). Making effective use of genomic sequence data. Trends Genet 15, 284-286. Wolfsberg, T.G. et al. (2001). Guide to the draft human genome. Nature 409, 824-826. Birney, E. et al. (2001). Mining the draft human genome. Nature 409, 827-828.