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Sponsored by the U.S. Department of Energy Human Genome Program
Human Genome News, January 1998; 9:(1-2)
Genes, which are housed in the DNA of the cell's nucleus, contain codes that essentially are recipes for tens of thousands of proteins. The code-containing regions of the gene (exons), however, are often separated by much noncoding DNA (introns). A cDNA molecule is a laboratory-made version of a gene that contains only its information-rich regions; these molecules provide a way for genome researchers to fast-forward through the genome to biologically important areas.
cDNA molecules are made using molecules of RNA (similar to DNA) obtained from living cells. In the cell, expression of the information from DNA into a protein first requires transcription of DNA into nuclear RNA molecules. These nuclear RNAs have noncoding regions that are processed out in the course of forming cytoplasmic RNAs (messenger RNAs). Because mRNAs are too fragile to withstand laboratory manipulations, scientists make sturdy double-stranded copies called complementary (or copy) DNAs, or cDNAs.
All DNA clones derived from a particular tissue constitute a library of clones representing the genes that were expressed when the source tissue was harvested. The analysis of libraries from many different tissues, obtained under a variety of physiological conditions, will be necessary to decipher the organ-specific patterns of gene expression.
The electronic form of the newsletter may be cited in the following style:
Human Genome Program, U.S. Department of Energy, Human Genome News (v9n1).
The Human Genome Project (HGP) was an international 13-year effort, 1990 to 2003. Primary goals were to discover the complete set of human genes and make them accessible for further biological study, and determine the complete sequence of DNA bases in the human genome. See Timeline for more HGP history.