Fruit Fly Larvae Identification Science Fair Projects

Stages of Life

Insects are a lot of fun to work with in science fair projects. It is very interesting to note the differences in their bodies and behaviors when they are in their various stages of life.

DNA Extraction	Student's Microscopes

Objectives/Goals

My goal was to design a method for identifying transgenic lacZ positive fruit fly larvae by their appearance, using a reporter gene assay. I used the E. coli gene set Lac Operon, which produces the beta galactosidase enzyme. A compound called 'X-Gal' reacts with beta galactosidase to produce a blue color. The blue color is used to detect gene activity in the transgenic organisms. In fruit flies and other eukaryotes, the blue color can only be detected after the organism is killed, and stained with X-Gal. This then eliminates the possibility of 'in-vivo' studies.

I had watched my father staining the dead flies, and wondered if there was a way to 'stain' the live ones. My hypothesis was that transgenic Lac Z positive fruit flies could display blue color (gene activity) if X-Gal was in their diet. The right concentration of X-Gal and beta galactosidase might produce live larva displaying the blue color. This would then permit in-vivo research!

Methods/Materials

My experiments involved growing strains of LacZ positive flies (D91, D105, & F273) with varying concentrations of X-Gal in their diet, totaling over 300 flies in my experiment. I also performed a control study using wild type flies cultured in the same media. The fly vials were observed under a dissecting microscope to look for larvae with any signs of blue color. 60 vials were prepared using X-Gal concentrations of 0.4 ppm, 2ppm, 4 ppm, 8 ppm, 10 ppm and control (no X-Gal). Each vial had a minimum of 2 pairs of flies.

Results

In the experiment, it seemed that a few of the experimental larvae/pupae expressed blue colored areas, indicating expression of beta gal enzyme.The results showed promise, but more specialized equipment will be needed to clearly view the blue color.

Conclusions/Discussion

Although the outcomes of the first experiment yielded inconclusive results, I was able to conclude that the Lac Operon is possibly only active during the pre-pupa to pupa stage. The pupae expressed the Lac Operon in the abdomen and tail areas, and survived in concentrations from 0.2ppm to 0.8ppm. This showed me that at these concentrations of X-Gal, transgenic screening through phenotypic detection was possible. Unfortunately, I was unable to develop a reliable screening method for LacZ positive fruit flies, but I have demonstrated that it is possible. I will continue my experiments, and hopefully, a new screening method will be available soon! 3rd party contributor