Drosophila Melanogaster Lab Report

The purpose of this experiment was to determine if there is natural selection against blind, white-eyed male Drosophila melanogaster, as well as if there is any interplay between selection and drift occurring in populations of different size. This was done by creating and monitoring both small and large populations and placing them in an environment with regular light or complete darkness. It was predicted that natural selection would occur against white-eyed males in the light trials, but would not occur in the dark trials. This selection would occur on the level of male mating success and be seen in a decline in the frequency of Q in the light trials. It was also predicted that drift would be larger in small populations, which would be seen

The results of the male mating success calculations however, were consistent with the prediction that selection would occur against white-eyed males in the light condition, but not in the dark condition. Results of viability calculations, white allele frequency over time, variance over time, and heterozygosity over time, were all inconsistent with predictions made. There was no statistically significant difference found between the viability of white and red flies in either lighting conditions, a result that was expected for the light condition but not for the dark condition, where selection was expected to occur against the white allele and decrease viability compared to wild-type males. The average allele frequencies behaved as predicted for the light treatment populations, showing a decrease in white allele frequency, most likely due to selection against the allele. The small/dark population also behaved as predicted, showing an increase in allele frequency, but the large/dark population showed an average decrease in allele frequency. Variance in the white allele frequency over time did not deviate from the Wright-Fisher model for any of the four treatment types. This trend was predicted for the dark treatments, but deviation due to selective disadvantage was expected to occur in the light treatments. The same phenomenon occurred in the calculations of heterozygosity over time. None of the populations showed statistical difference from the Wright equation calculated values, which was expected for the dark treatments but not for the light populations. These inconsistencies between predictions and results may be due to selective disadvantage against the white allele under light conditions and the effect of population size not being as strong originally hypothesized. The unexpected results may also be due to the high