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.
Recognizing various structures of the adult organism, especially sexual differences, will be important in carrying out the experiments to follow. For both male and female flies, locate the head, thorax, and abdomen, the mouth parts (particularly the extendable proboscis), the aristae (feather-like antennae), and the compound eye made up of many individual facets called ommatidia (singular, ommatidium).
The eggs are about 0.5 millimeters (mm) in length and bear a pair of filaments at one end that keep them from sinking into the soft food on which they are usually laid. The larvae are small maggots that burrow in the food and spend most of their time eating. Drosophila larvae pass through two molting stages called instars, where they shed their outer protective cuticle, and finally reach a size up to 4.5 mm in length. After their second molt, the larvae crawl off the food onto a dry spot on the container wall where they pupate into small dark cocoons. At 25oC, metamorphosis takes about four days after which the adult fly emerges. At first the adult is somewhat pale in color, its wings are crumpled, and its sex is difficult to distinguish. But within a few hours the wings expand to full size and the adult coloration is visible. Female fruit flies remain virgins for about six hours after hatching but will mate freely thereafter. Females that are allowed to stay in containers with males when they are older than six hours cannot be considered to be virgins as they have probably mated with one of the males in the container. For this reason flies are separated before or immediately after birth so that only planned matings will occur during experiments. The objective of this lab was to determine the mode of inheritance of a specific mutant phenotype. We observed that our mutant flies displayed a mutant phenotype in eye color. The mutant flies exhibited a white-eyed phenotype whereas the wild type flies presented a red-eyed phenotype