The fruit fly is a convenient organism for genetic studies because a single mating produces hundreds of offsprings, and also, a new generation can be bred every two weeks. A second advantage of the fruit fly is that it has only four pairs of chromosomes which are easily distinguishable under a microscope. Furthermore, their life cycles can be successfully maintained in a small vial containing a simple food source, numerous traits with two or more expressions are present and lastly, the salivary glands contain giant « polytene » chromosomes that facilitate cytogenetic research. Drosophila, of the order DIPTERA has a life cycle of four stages.
1-EGG : The diploid zygote develops by mitosis into the larva.
( worm like form), which hatches one day after the egg is laid.
2-LARVA : The larva is enclosed in a relatively inflexible body covering which appears to feed continuously. In order to grow, it must get rid of this covering and develop a larger « coat ».The period from the fertilization to the third larva stage last about 5 days. The three stages are separated by two periods of molting where prior to the last one, the larva moves to a drier location and becomes sedentary. Its covering gets harder and then, the insect develops its new coat and become known as the .
3-PUPA : In this stage, the larval tissues are all destroyed and new tissues are built to form the winged adult.
4-ADULT : The adult fly will emerge from the pupa approximately 10 days after the fertilization of the egg. It will be ready to engage reproductive activity 12 hours after its emergence. In our experiment, we perfomed two crosses between two different phenotypes. Wild-type females x Vestigial males and vestigial males x wilt-type females. According to Mendel, traits that that are alternatives to wild-type, such as vestigial wings, are called mutant phenotypes. As a matter of fact, this experiment is done to see whether our mutant phenotype (vestigial wings) is x-linked or autosomal.