Approaches to Studying Quantitative Traits in Drosophila melanogaster

Quantitative or complex traits do not follow discrete Mendelian phenotypic patterns but rather display a continuous range in their phenotype. Both genetic variation due to the effects of multiple genes and their alleles and environmental variation contribute to these traits’ phenotypic variation. In humans, quantitative traits are studied through the use of genome wide association studies which associate genetic variants with variation in these traits. Many model organisms such as Drosophila melanogaster offer many advantages for studying quantitative traits due to the control over both environmental and genetic variation these systems provide and the ease of maintaining and testing many individuals. Here we present three separate projects using D. melanogaster to study a variety of quantitative traits using various techniques and benefiting from the many advantages this model provides. Chapter I presents an Extreme QTL mapping study identifying areas of the fly’s genome associated with variation in zinc toxicity resistance. Due to the ease of being able to test thousands of flies per replicate and having control over the selective pressure we exerted onto them we identified 7 loci associated with toxicity resistance. Chapter II follows up on the results from Chapter I by testing zinc toxicity resistance on mutant and wildtype lines and utilizes aspects of their genetic backgrounds to limit environmental variation by having lines tested within the same vial. Chapter III focuses on a different quantitative trait, aging, and due to the flies’ shorter lifespans we could characterize gene expression trajectories over the course of the adult lifespan. Genes were then clustered together using these expression trajectories and a series of enrichment analyses were conducted to see if these clustered genes shared similar functions. While each of these projects used a different approach to study these quantitative traits, they all capitalized on the control over genetic and environmental variation that D. melanogaster affords and the ease of testing individuals.