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genetics of diploid organisms

Fruit Fly Biology & Culture: Fruit flies are fairly easy to culture in the laboratory; only a few specialized materials and some basic skills are required to use them successfully in genetics studies. Here is a short guide to the biology and culture of Drosophila melanogaster. Fruit Fly Life Cycle: Drosophila melanogaster has complete metamorphosis life cycle with an egg, 3 larval instars, pupa, and adult. If cultures are maintained at 21 ˚C, it takes an average of two weeks between when the flies are mated and when their offspring emerge as new adults. Development time is a couple of days shorter if the temperature is 23 ˚C. FIGURE 32. Life cycle of Drosophila melanogaster. From the Carolina Drosophila manual, Carolina Biological Supply. Adults are ready to mate within 8 to 12 hours after they emerge and can live under laboratory conditions for more than a month. Females begin laying eggs within a two days after mating and first-instar larvae are active within three to four days. These soft-bodied larvae grow rapidly as they crawl through rotting fruit eating fungi and bacteria. In the lab, we will culture them on an instant medium developed by the Carolina Biological Supply Company. Larval flies can almost be considered aquatic, because they require a moist environment in which to survive. They continue to grow and molt through two additional larval instars before seeking a drier place to pupate, usually on the side of the culture tube. The pupal stage lasts for approximately six days. Shortly before emergence, the pupae darken and the wingpads become visible as two small black spots. Adult flies emerge through small openings on the anterior end of the pupal cases. Newly emerged adults are pale, skinny, and their wings shriveled. It takes an hour or so before their abdomens become round and their wings expand