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Page 2 Introduction Drosophila melanogaster is an excellent organism for use in the study of genetics. Its small size, relative ease of maintenance, short life cycle, and its ability to produce many offspring have lent it to the demonstration of Mendelian inheritance in every location from the elementary school to the university laboratory. From the thousands of available strains, we have selected an assortment of forty types, which serve most purposes. The basic requirements for growing and working with Drosophila are as follows: I. Media Many different types of media have been used for the culture of Drosophila. The simplest is just a slice of banana. However, each medium has its drawbacks. In order for a medium to be useful, it must be solid and dry enough so the adult flies do not drown, and it must inhibit the growth of molds, which are almost always present on the flies and in the air. II. Handling Flies Materials needed for working with flies are: a Petri dish, an ice pack or cryolizer, a magnifying device (binocular dissecting microscope, large magnifying glass, etc.), a light (goose-neck desk lamp, a microscope lamp, etc.), a camel's hair brush, a white viewing surface, and a "morgue" bottle (any bottle with a cap, partially filled with alcohol, mineral oil, etc. into which dead flies and those to be killed can be dropped). Put the culture of flies in a refrigerator on its side so that the flies will not be trapped in the media. After 20 minutes or so check the cultures to make sure the flies are unconscious. Then tap the flies into a Petri dish. Using the camel's hair brush, separate the flies into different groups (e.g., males and females; red eye and white eye, etc.) In preparing a new culture, five to ten pairs of flies should be used. It is not difficult to distinguish between the male and female Drosophila. With a little practice, the difference can be seen without magnification (refer to Figure 1). The female is usually slightly larger than the male. The abdomen of the male appears to have a distinct black tip and a blunt posterior, while the female has a somewhat lighter and pointed posterior with bands visible almost to the tip. The male also has sex combs on the front legs and the female does not. As the female becomes older, her abdomen becomes distended with eggs, making identification even more simple. Working with Drosophila Introduction Figure 1 Female Male