DNA sequencing. Computer image of a coloured auto- radiogram showing sequenced cDNA (complementary DNA), from a 32-lane electrophoresis gel. Colour bands correspond to base pairs that form the code for a section of cDNA. This is part of research at The Institute for Genomic Research (TIGR) in Gaithersburg, Maryland, USA. Here scientists analyse the structure and function of human genes, and animal & plant genes for comparison. At TIGR, cDNA ESTs (Expressed Sequence Tags) are produced; these tags" enable the reading of cDNA, lengths of copied genetic material identical to genes. Mapping human genes will enable the development of genetic therapies for inherited human diseases."