Drosophila Experimental Study

In the present study, the frequency of white allele in Drosophila melanogaster was observed to determine if natural selection or drift occurred in the experiment. By studying the allele frequency under 2 different conditions (dark/light, small population/large population), we predict the fitness of white allele is lower in the light environment compare to the dark environment where no natural selection occurs. Thus, the variance would be larger in dark population compare to the light population. In addition, selection would play a larger role in large population size, whereas more drifts can be found in small populations. Moreover, the change in heterozygosity would be bigger in small population compare to the large population.
Based on our

However, in our experimental data, all groups except small population under light treatment increases their variance. The decrease of variance among small/light group could be due to the selection on the relative fitness of the two phenotypes of Drosophila. An increased fitness of wildtype red-eyed allele would more likely be favoured by natural selection in light environment, while the white-eyed allele would be strongly unflavoured and selected against in the light setting. Moreover, fixation is possible to occur among small populations under the light environment and leads to the decreased variance of white allele. Although males are more favoured under the light environment as they are more easily to find a mate, the white-eyed allele are more easily to reach fixation among small population with the effect of drift. Hence, except for the decline in white allele frequency among small population under light treatment, other groups all follow the pattern of Wright-Fisher expectation as their variance of allele increases over generations. Meanwhile, the calculated Wright’s expectation for change in heterozygosity decreases in both small and large populations. In our calculated data, small populations under light treatment is the only group that has an increased change in heterozygosity. This could due to the physiological differences between the mutant ad wildtype flies or sampling error. In addition to the two evolutionary forces, non-random natural selection and random genetic drift might also have an