Student Research Projects

Genetic Recombination in Wolbachia-Infected Drosophila melanogaster

Student William Lawson '16 (Biology and International Studies)
Faculty Mentor(s)
Department Biology
Course Biology 489: Research in the Natural Sciences


Wolbachia is a genus of bacteria that are commonly found infecting many different species of invertebrates, especially insects. Previous work at VWC with a locally-collected, Wolbachia-infected strain of fruit fly, has demonstrated that flies harboring this ensosymbiont produce fewer offspring, have an altered microbiome and, possibly affect the outcome of genetic crosses. Specifically, there was noted a dramatically increased rate of crossing-over in male flies; an event known to be very rare. This research sought to extend these initial observations showing significantly different phenotypic ratios in crosses, by repeating them on a larger scale. Wolbachia-infected and uninfected strains were crossed with triple-mutant apterous, brown and sepia flies. The F1 progeny were backcrossed to the triple mutant line to detect both recombination between the linked genes apterous and brown, and the independent assortment of the sepia gene. A PCR assay for the Wolbachia-specific wsp gene was used to confirm the infection status of the flies and to demonstrate the maternal inheritance of the endosymbiont. The results of the crosses are not consistent with previous observations in that extensive crossing over was detected in both infected and uninfected male flies. Additionally, skewed ratios involving both infected and uninfected females were also seen. At this point, it is unclear if the increased rate of crossing over in male flies is due to Wolbachia, or due to other genetic differences between the locally-collected ‘wild’ wild-type strain and the stock strains from which the triple mutant is derived. Further crosses, generating even larger numbers of progeny flies, are required to reconcile these observations with previous work.