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                       A Gene Map of the Human Genome

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 The Human Genome Project is expected to produce      Genome Maps 1996
 a sequence of DNA representing the functional       Show Featured Genes
 blueprint and evolutionary history of the human
 species. However, only about 3% of this sequence          [Image]
 is thought to specify the portions of our 50,000
 to 100,000 genes that encode proteins. Thus an      Credits / Abstract /
 important part of basic and applied genomics is          Glossary
 to identify and localize these genes in a
 process known as transcript mapping. When genes     Browse by Chromosome
 are expressed, their sequences are first                1 2 3 4 5 6
 converted into messenger RNA transcripts, which       7 8 9 10 11 12
 can be isolated in the form of complementary         13 14 15 16 17 18
 DNAs (cDNAs). Approximately half of all human         19 20 21 22 X Y
 genes had been sampled as of 15 June, 1996.

 A small portion of each cDNA sequence is all
 that is needed to develop unique gene markers,      Research Tools Page
 known as sequence tagged sites or STSs, which
 can be detected in chromosomal DNA by assays
 based on the polymerase chain reaction (PCR). To
 construct a transcript map, cDNA sequences from
 a master catalog of human genes were distributed
 to mapping laboratories in North America,
 Europe, and Japan. These cDNAs were converted to
 STSs and their physical locations on chromosomes
 determined on one of two radiation hybrid (RH)
 panels or a yeast artificial chromosome (YAC)
 library containing human genomic DNA. This
 mapping data was integrated relative to the
 human genetic map and then cross-referenced to
 cytogenetic band maps of the chromosomes.
 (Further details are available in the
 accompanying article in the 25 October issue of
 SCIENCE).

 The histograms reflect the distributions and
 densities of genes along the chromosomes.
 Because the individual genes (>16,000) are too
 numerous to represent, images have been chosen
 to illustrate the myriad aspects of human
 biology, pathology, and relationships with other
 organisms that can be revealed by analysis of
 genes and their protein products.

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The Gene Map web site is hosted by
the National Center for Biotechnology Information,
National Institutes of Health, Bethesda MD 20894, USA.

Send comments and suggestions to info@ncbi.nlm.nih.gov