The History of Drosophila Melanogaster in Science how the Fruit Fly Revolutionized Genetics

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Drosophila melanogaster, or the common fruit fly, has made a most uncommon contribution to modern science. Thanks to its rapid life cycle and versatile genetic code, it is one of several key model organisms used in laboratories to run multi-generational experiments on genetic manipulation and adaptation.

The common fruit fly belongs the flies order (Diptera), and the Drosophilidae family. In the wild (i.e. outside of certain carefully bred and manipulated stocks) they are small with red eyes. Females are larger than males and lack a black abdominal patch noticeable on the males of the species. The lifespan of a fruit fly is approximately one month, although its maturation varies based on conditions: heat stresses young fruit flies and delays their growth. Females lay hundreds of eggs at a time, usually into decaying food sources like fruit, and the young take about four days to grow into adults.

This has made Drosophila melanogaster unusually attractive to modern biologists. Fruit flies can easily be grown in large numbers at low costs in the laboratory setting. Some time ago now, scientists were excited to learn that they also had an unusually simple genetic code with just four pairs of chromosomes. Taken together, this means that fruit flies are easy to breed for multiple-generation experiments studying natural adaptation and genetic evolution, and it is comparatively easy to manipulate their genetic code and then monitor the effects of such changes. Its genome was sequenced in 2000, making it (along with other model organisms, like C. elegans) one of the first animals to complete the sequencing process.

Historically, these factors together meant that Drosophila melanogaster revolutionized genetics. The first systematic fruit fly experiments began in 1910 at Cambridge, in the laboratory of Thomas Hunt Morgan. In a simplistic laboratory (generations of fruit flies hatched, lived, and died in milk bottles, monitored under handheld lenses), Morgan and his students made some of the most important early empirical studies on heredity and alleles, studying how fruit flies inherited some traits and not others from their parents. According to Hobart and William Smith Colleges, these studies confirmed earlier work in plants by Gregor Mendel, identifying (even before scientists actually understood the existence or importance of DNA itself) that traits were hereditary and that certain traits were always either dominant (always expressed if passed on by either parent) or recessive (expressed only if passed on by both parents).

In the 1930s, according to Martin Brookes, Theodosius Dobzhanksy took this a step further by studying large populations of flies in the wild, noting in his American studies that, as the theory of evolution predicted, genetic drift and differentiation occurred over time when populations of the same species were separated from one another. Finding large-scale changes in complex species required long-term surveys of the fossil record, but the fast-breeding fruit flies held out another option: studying minor but noticeable differences over very short periods of time. Dobzhansky began with the observation that his fruit flies could be traced back to specific regional populations by the color bands on their abdomens.

The fruit flies' legendary biological value continues to attract researchers today. There is still an annual Drosophila Research Conference, devoted specifically to genetic and biological research involving fruit flies. As our knowledge of the human (and animal) genetic code grows ever more advanced, these studies have transformed from basic studies of heredity into highly sophisticated experiments in gene therapy. One project reported on by PhysOrg, for instance, was able to identify a key protein in human kidney cancers using fruit fly tests, paving the way for new detection techniques and possibly even new targeted therapies for that deadly disease. Others claim that fruit fly research will one day yield insights into sleep patterns, mental illness, and sexual orientation, as well, although these are still more speculative.

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