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1999 - 2000
The Drosophila genome
Experiments with the common fruit fly, Drosophila melanogaster, established the chromosomal theory of heredity in 1912. During the rest of the twentieth century Drosophila became a model organism for experimental geneticists who bred and crossbred it extensively. An abundance of knowledge about the fundamental mechanics of genetic variation and hints about specific traits was generated from Drosophila research. The fly's complex chemistry, with genetic counterparts to many human diseases, including various forms of cancer, made it interesting and useful. Discoveries stemming from work with Drosophila led to three Nobel Prizes.
The Berkeley Project had already completed sequencing about one-fifth of Drosophila melanogaster's genome when Celera offered to complete the job, more quickly and without financial compensation, as a trial for its human genome sequencing effort. After sequencing, the BDGP would close remaining gaps and use its considerable database to annotate the genome and produce a detailed physical map. (The map would also serve to check the accuracy of Celera's work.) The entire genome was made public without restriction. The sequencing of Drosophila, begun in May 1999, was completed in September of that year. Assembly took place over the next four months and was finished in December. A comprehensive article appeared in Science on March 24, 2000. Combined with nine decades of accumulated knowledge, the fruit fly's genome immediately yielded an impressive new harvest of information. The Drosophila genome at first count revealed 13,601 genes. Thousands of these genes were entirely new to research, and their functions remain to be determined. But the most remarkable immediate outcome was the number of genes similar to human genes. A survey of 269 sequenced human genes, mutations of which were implicated in disease, showed that 177 of them had a closely related gene in the Drosophila genome. These included genes connected to neurological diseases, such as spinal cerebellar ataxia and muscular dystrophy; the p53 tumor suppressor gene and other genes related to cancer; and genes that affect blood chemistry, how the kidneys work and the immune-system functions. Because so many Drosophila genes are similar to those found in humans, Drosophila demonstrated the potential of comparative genomics for medical research.
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