Drosophila melanogaster (black-bellied dew-lover) a dipteran (two-winged) insect, is the species of fruit fly that is commonly used in genetic experiments.
The life cycle of Drosophila melanogaster
at 25 °C takes only 2 weeks. Females lay eggs (embryos) that eclose after 24 h. During oogenesis, cytoplasmic bridges connect the forming oocyte to nurse cells. Nutrients and developmental control molecules move from the nurse cells into the oocyte. In the image shown (to left), the forming oocyte can be seen to be covered by follicular support cells. The resulting larvae
grow for 5 d while molting
twice, at about 24 and 48 h after eclosion, before encapsulating in the puparium and undergoing a five-day-long metamorphosis
Females first mate about 8 hours after emergence. The females store sperm from previous males they mated with for later use. For this reason geneticists must collect the female fly before her first mating, that is, a virgin female, and ensure that she mates only with the particular male needed for the experiment.
Drosophila melanogaster was chosen as a genetic animal model at the beginning of the twentieth century by Nobel Prize winner Thomas Hunt Morgan. Since then it has been a very successful animal model for biological research, for several reasons:
- It is small and easy to grow in the laboratory.
- It has only 4 chromosomes.
- Males do not show recombination, facilitating genetic studies.
- Genetic transformation techniques have been available since 1987.
- Its compact genome was sequenced in 1998.
In the molecular biology
geneticists are known for their relatively whimsical naming of discovered gene mutations. Compared to the stodgy (but perhaps more practical) "cdc4", "cdk4", etc. names in the yeast
sports such favorites as "cheap date" (a mutation leading to increased sensitivity to ethanol intoxication) and "snafu" (a mutation leading to grotesque anatomical abnormalities).