Drosophila Melanogaster

Resources

Throughout the nineteenth century and for the first half of the twentieth century, the fruit fly Drosophila melanogaster, was the principle tool for genetic studies in eukaryotes. These studies provided the basis of much of our understanding of fundamental aspects of

eukaryotic genetics. Discoveries have shown that the conservation of genetically-determined traits between the fruit fly and mammals is much greater than ever expected, from structure proteins to processes such as development, behavior, sleep, and other physiological responses.

Drosophila melanogaster, is a tiny fly, only 0.08–0.12 in (2–3 mm) in length and is often found around grapes and rotten bananas. Their small size also means that a large number of Drosophila can be maintained in a research lab without occupying a great deal of space. Another virtue is that they reproduce frequently, furnishing a new generation in less than two weeks; each generation includes hundreds of offspring. Flies that express a gene mutation will thus be apparent in a short time. They are also easily and inexpensively maintain, and are easy to examine. These attributes have made them a valuable research tool. All these characteristics make the fruit fly an ideal model for genetic studies.

In 1903, T. H. Morgan started his work on heredity and chromosomes using the fruit fly. In 1910, Morgan published his famous paper “Sex Limited Inheritance in Drosophila” in the journal Science that described a white-eyed male fruit fly mutant he observed and the crossing experiments he conducted in his laboratory. The research of Morgan and his associates demonstrated that genes for specific traits were located on separate chromosomes. Genes were arranged in a linear order and the relative distance of genes could be determined experimentally. These studies in the first third of the twentieth century established the chromosome theory. Morgan was awarded the Nobel Prize in 1933 for his discoveries on the research of the fruit fly.

The larval stage salivary gland chromosomes of the fruit fly are called polytene chromosomes. They are unique morphologically. The size and length of the chromosomes are greatly increased due to numerous rounds of replication. This can be seen easily under the microscope. In 1934, T. S. Painter of the University of Texas published the first drawing of the fruit fly polytene chromosomes, which included the chromosomal localization of several genes. In 1935 and 1938, C. B. Bridges published the fruit fly polytene maps. His maps were so accurate that they are still used today. These are the pioneer work on physical gene mapping.

The fruit fly genome sequence was the second organism sequence to be determined. The fruit fly has four pairs of chromosomes. The whole genome is about 180 million base pairs. There are about 14, 000 genes in the genome. Since the release of an initial draft sequence in 2000, scientists at the Berkeley Drosophila Genome Project (BDGP) and Celera (a private genomic company) continue to release improved versions of the Drosophila genome sequence. The latest version, (Release 5) was released in March, 2005. An update to the sequence was released in April, 2006.

Resources

BOOKS

Hubbell, Sue. Shrinking the Cat: Genetic Engineering Before We Knew About Genes. New York: Mariner Books, 2002.

Johnson, Rebecca L. Genetics. Minneapolis: Lerner Publications, 2005.

Snustad, D. Peter and Michael J. Simmons. Principles of Genetics. New York: John Wiley & Sons, 2005.

PERIODICALS

Celniker, S.E., et al. “Finishing a whole genome shotgun: Release 3 of the Drosophila melanogaster euchromatic genome sequence.” Genome Biology. 3(12) (2002).

Hoskins, RA., et al. “Heterochromatic sequences in a Drosophila whole genome shotgun assembly.” Genome Biology. 3(12) (2002).

Xiaomei Zhu