Student Research Projects

Influence of Wolbachia Infection on Fruit Fly Crosses

Student Riana Garcia ‘16 (English and Psychology)
Faculty Mentor(s)
Department Biology
Course Biology 489: Research in the Natural Sciences


Wolbachia is an obligate intracellular bacterial endosymbiont commonly found in many insect species, including a locally collected strain of the common fruit fly Drosophila melanogaster. This project involves discovering the influence of Wolbachia infection on fruit fly crosses. The goal is to resolve the conflicting results of previous work done with this system at Virginia Wesleyan College. Previous research indicated skewed gender ratios and anomalous crossing over in male fruit flies, something that is known to occur only rarely. Subsequent independent research did not confirm these results. This project utilized two different Wolbachia-infected strains (wild type and the wingless mutant apterous) and compared them with their Wolbachia-free counterparts. The infection status of the fruit flies was first verified by PCR. Infected males were crossed with uninfected triple mutant (apterous, brown, sepia) females and vice versa. The F1 progeny were observed to determine gender ratios. Testcrosses were performed using the F1 progeny and the progeny's phenotype was determined. No effect on gender ratios was seen in F1 progeny. Analysis of the expected phenotypes of over 1,400 test cross progeny, derived from F1 males, failed to demonstrate significant crossing over (only one recombinant fly was detected). A similar analysis of over 1,900 test cross progeny, derived from F1 females, revealed significant deviations from the expected proportions of recombinant phenotypes but this did not correlate with Wolbachia infection status. It is concluded that Wolbachia has no significant effect on either gender ratios or crossing over in our strains of flies.