Drosophila melanogaster commonly known as the fruit fly is considered a model organism in the field of genetics because of its short life cycle of about 10 weeks and the ability of the fly to produce a relatively large number of offspring at 50-70 eggs per day upon female maturity. The physical size of the male and female Drosophila is approximately 2.5 to 3 mm respectively Drosophila allowing for minimal storage space in a laboratory setting. The intricate nervous system of the fruit fly has made them very vital to genetic research in nervous system disorders and cancer research (Klug, 12). The goal of the Drosophila melanogaster lab was to breed homozygous wild-type Drosophila melanogaster with homozygous mutant Drosophila melanogaster (the P1) to produce the F1 offspring from a monohybrid cross. The F1 offspring mate and produce the F2 generation. Two known homozygous mutant fly types were crossed (dihybrid cross) in the P1 generation to produce the F1 offspring. The F1 generation produced the F2 generation dihybrid crosses. After each generation the offspring were counted and observed for specific phenotypic characteristics, including sex and the data collected for comparison. Four mutant Drosophila melanogaster were selected by the team from a list of acceptable combinations of Drosophila mutants and wild-types to create the 2 monohybrid crosses and 2 dihybrid crosses. The first monohybrid cross (cross 1) contained Oregon-R and cinnabar mutant flies. The second monohybrid cross contained Oregon-R and white mutant flies. The third cross was a dihybrid cross between the cinnabar mutant and the dumpy mutant fly. The final dihybrid cross contained the white mutant and yellow mutant fly. The data obtained from the crosses will provide dominant and recessive traits, a pattern of inheritance, as well as potential for autosomal and sex linked traits. Methods:
1. Four vials with sponge plugs were obtained and labeled with the group name, cross number, lab number, and date. 2. Each vial was prepared with a culture containing food prepared by adding 1 scoop of food, and equal amount of water, and a pinch of yeast and allowed to sit for several minutes. 3. Separate vials containing virgin female and male flies of the Oregon-R wild-type were obtained 4. The flies were anesthetized by dipping an absorbent wand into a bottle of Triethylamine (fly nap). 5. The excess Fly nap on the wand was blotted onto a paper towel. 6. The wand was then placed into the vial containing Oregon-R wild-type flies just below the sponge stopper for approximately 60 seconds. 7. The anesthetized flies were removed from Oregon-R vial and place onto a white piece of paper. 8. Using a dissecting microscope the male and female flies were separated according to the following guidelines of Genitalia Differences listed in table 1.
Smaller 2.5 mm| Usually larger|
Dark blunt abdomens| Lighter colored pointed abdomens|
Last segment of abdomen is solid black| Abdomen is striped to the end| Sex combs-black bristles on upper joint of forelegs| No sex combs| Table [ 1 ] Genitalia Differences
9. Six male Oregon-R D. melanogaster was placed into each of the vials labeled P1 Cross 1 and Cross 2. 10. The sponge stopper was placed in the open end of the vial and then the vial was placed on its side to prevent the flies from suffocating in the food medium will asleep. 11. Steps 3 through 5 were repeated for the mutant fly male Cinnabar and female Dumpy for the P1 dihybrid Cross 3 and the sponge stopper was placed in the vial and the vial placed on its side. 12. Steps 3-5 were again repeated for the dihybrid cross of the male white mutant and the female yellow mutant and placed in vial 4.
CROSS NUMBER| VIAL NUMBER| MALE TYPE| FEMALE TYPE| GENERATION| 1| 1| Oregon R wild-type| Cinnabar mutant| P1|
2| 2| Oregon R wild-type| White...