Drosophila Melanogaster Experiment

Testing Genetic Drift and Natural Selection in Drosophila melanogaster Materials and Methods

The materials and methods are from (Welsh and Thompson 2016)

Wild-body type (tan) and ebony body type Drosophila melanogaster were prepared before this procedure by chilling the flies to leave them immobilized . Drosophila melanogaster is an ideal organism for this experiment for they can be easily cultured. They can be cultured in less space in a temperature of 21-25(degree Celsius find degree sign), they have a short generation time of approximately two weeks and they are large enough to be seen with the naked eye and observed clearly with a dissecting microscope.

To prepare the small population, ten to twenty randomly chosen wild type (tan)

At week two the culture vial containing the smaller population, that began with eight flies, was taken and as many flies as possible were aspirated into a transfer vial which was then chilled for at least seven minutes. These flies were placed on sorting plate than randomly the first four females and first four male flies were taken as the parents for the next generation. The phenotype of the randomly selected "parent" flies were recorded in our data sheets. Once the flies were chilled and fully immobile they were transferred using weigh paper to the culture vial, again keeping the vial laying horizontally until they regained consciousness. This culture vial was then labelled with population size and group name. Once small population was complete, the same procedure was replicated but for the larger population, where the first twenty male flies and first twenty female flies were randomly selected to be parents for the new generation of the large population. The excess flies not used for the new generations were disposed of . Once new vials were completed the F1 phenotypes were counted to calculate allele frequencies and expected heterozygotes (2pq) and recorded. After this for the next four weeks random samples of both the small and large population were taken, the phenotypes of this random sample were counted and used to calculate the allele frequencies; all data was recorded. Allele Frequencies using Hardy Weinberg equation p2+2pq+q2= 1, where: p=0.5 (began equal number of flies with each trait), frequency of ebony body flies= q2, frequency of ebony body allele= q and frequency of wild type allele= p= 1-q. Computing the Heterozygosity present in populations,