THE GENETICS OF FRUIT FLIES

This lab’s purpose was to determine the genetics of fruit flies, including but not limited to: raising them, feeding them, mating them, sexing them, separating them, and mating them again. We then had to determine which traits were dominant in flies, in my case either the wild eyes or the white eyes, by crossing the flies and through phenotypic ratios we were to determine genotypes. My partner was Eugene Montoya. We chose the white flies because they were more attractive than the Sepias, and there’s nothing I hate more than an ugly fruit fly.

Eugene and I had some difficulties raising, and crossing our fruit flies. A number of problems arose throughout our experiment. After we raised our cultures and attempted to sex them, we had difficulty telling which sex they were due to the fact that some males were in their very early stages of development out of the pupi and had not developed the black tip covering their posterior yet. We also encountered problems when mating flies. When we put the flies together they would not mate. On more than one occasion our flies died before they had sex for some reason, possibly the Fly Nap made them sterile (or it could’ve been the LSD I fed them), but for some reason our flies just didn’t get horny. In order to obtain results, I visited the Virtual Fly Lab online at http://vcourseware4.calstatela.edu and designed a theoretical cross between a wild male and a white female, and a white male with a wild female. Results were as follows:

Pure Wild Male X Pure White Female: 1:1 ratio of Female Wilds to Male White with no Female whites or Male Wilds. We then mated the F1 generation Female Wilds and Male Whites and got the following results: 1:1:1:1 ratio of Male Wilds, Female Wilds, Female Whites and Male Whites.

Pure White Male X Pure Wild Female: 1:1 ratio of Female Wild and Male Wild with no whites at all. We then mated the F1 generation Female Wilds and Male Wilds and got the following results: 2:1:1 ratio of Female Wilds to Male Wilds to Male Whites.

Due to the fact that the pure female Wild X pure male white resulted in only wild flies, led us to believe that the trait for Wild or White was a sex-linked trait. Then looking at our other results, we inferred that the Wild gene must be dominant, because a heterozygous female had to result from the cross of a wild female and a male white, yet only wild traits showed up. This proved that the allele for White eyes is recessive to the allele for Wild eyes, and we concluded that eye color is a sex-linked gene. It would’ve been nice to be able to cross our flies and sex them perfectly using our own results to determine our conclusion, but we learned that in science everything does not always go as planned, and that human error is a major factor in every experiment I will ever attempt. I gained many things from this expirement, including knowledge of human error, and our lack of control over nature's functions. Although in theory something may be easy as cake, in practice it is a bit more difficult and there are more difficulties than expected. In future labs I will have to account for these factors before hand in order to achieve as accurate and precise results as possible. I enjoyed this lab very much, and I think it also tought everyone not only about the complicated genetics of Drosphilia Melanogaster but also taught us that responsibility is a requirement when doing science labs.

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