Fruit Fly Essay

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Genetic Crosses in the Fruit Fly Drosophila melanogaster

Introduction
Since the turn of the 20th century, Drosophila melanogaster, the common fruit fly, has been a useful organism for the study of genetics. Its relatively short generation time (approximately 10 days at 25oC) yields a large amount of breeding data in a short period of time. Because of its simple food requirements and easy handling in the laboratory, large and varied stocks of Drosophila can be maintained with minimal cost and effort (Ashburner, 2008).
The general anatomical features of a male and female wild type fruit fly and the organism’s life cycle are shown in Figure 1. Recognizing various structures of the adult organism, especially sexual differences, will be important …show more content…

The entire developmental cycle takes about 14 days at 21oC (close to lab room temp). At higher or lower temperatures, the cycle is proportionally shorter or longer. Eggs are tiny, oval, white objects about 1 mm long with two long filaments at one end. Larvae hatch from the eggs about a day after they are laid. Larvae are white, segmented, worm-like burrowers with black mouthparts at their anterior ends and a pair of spiracles (short tubes) for tracheal breathing at both their anterior and posterior ends. Larvae vary from about 1-7 mm in length when ready to pupate. Since their cuticles (skin) will not stretch, the larvae periodically molt to reach adult larval size. There are two such molts during Drosophila development. Before and after molts, larvae are called instars; thus, the fruit fly has three instars. After the second molt, the third larval instars crawl from the medium onto the sides of the culture vessel and …show more content…

1. The last abdominal segment of the male is much larger and more rounded than that in the female.
2. The abdomen of the male contains only five segments while that of the female contains seven.
3. The male's body size is generally somewhat smaller than that of the female.
4. The male has a small, densely packed tuft of bristles known as a sex comb located on one of the outer joints of both forelegs. (The female lacks these).

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