Fruit Fly Lab Report

The purpose of this experiment was to conduct a long-term population genetics study by observing five generations of Drosophila melanogaster to determine the allele frequencies of eye color.

Population genetics is the study of distribution and change in allele frequency in a population (). This makes population genetics important to the study of evolutionary biology as it examines adaptations, speciation, and the population structure of a population under study (). Two important processes of population genetics that will be examined in this experiment are natural selection and genetic drift, both that are important to evolution (). For Natural Selection to occur there must be some level of variation among the population that is heritable.

For this experiment, the fruit fly was the species of choice since the fruit fly does not occupy a lot of space, can produce large amounts of offspring for each generation, and has an observable phenotypic trait such as eye color. There are four life stages of the fruit fly: egg, larva, pupa, and the adult stage (). Using a dissecting microscope, we can determine the sex of the fruit fly be either observing the abdomen or the legs for a sex comb (). For males, the abdomen is darker colored and rounded at the end, while females have a longer and bigger abdomen with black stripes (). Males also have a sex comb located on their front legs that can be used to determine their sex when it is difficult to separate from their abdomen color and size (). In general, males are also smaller in size than female fruit flies are

This means that the G0 female population had the genotype w+w+ for red-eyed and ww for the white-eyed fruit flies. On the other hand, male fruit flies only have one X chromosomes with the other sex determining chromosome is Y. Red-eyed males would have the genotypes w+Y and the white-eyed males would have the wY genotype. This means that when looking at the male fruit fly it can be easy to determine the eye color allele with the naked eye. Due to the gene being X-linked the allele frequency for both eye color alleles can be calculated for males, unlike females as a red-eyed female could have either the w+w+ or the w+w genotype ().The Hardy-Weinberg equilibrium states that the genotype and allele frequencies within a population will stay constant from each generation when there is a lack of evolutionary influences, such as genetic drift, mutation, and mate choice