Honors Theses

Investigating the Pleiotropic Potential of Known Genetic Switches that Regulate Gene Expression


Thomas Williams



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Honors Thesis


Animals build, organize, and maintain a diversity of cell types throughout development and adulthood. Cellular diversity results from the regulated expression of genes. Most genes are “pleiotropic” and are expressed in several cell types and/or during multiple developmental stages. Cell type and developmental stage-specific patterns of expression are switched on by cis-regulatory element (CRE) DNA sequences. In contrast to genes, CREs are generally assumed to function in a modular, or non-pleiotropic, manner. This assumption shapes the way CREs are thought to impact development, evolution, and genetic disease. However, the generality of CRE modularity has not been satisfactorily demonstrated, as it is difficult to test for CRE activity or inactivity in all cell types and during all developmental stages. The goal of this research was to explore whether some well-studied CREs possess pleiotropic gene expression-regulating activities. The research centered around the CRE called t_MSE, which regulates male-specific expression of the Drosophila melanogaster tan gene as a part of a program to develop melanic cuticle plates on the posterior abdomen. In this thesis, I give an account of my studies which did not find a pleiotropic activity for t_MSE and which share a cautionary tale of how experiments studying CRE function can provide false positive results. In the future, studies should investigate additional potentially pleiotropic CREs to better gauge whether CRE pleiotropy is rare or common. The outcomes will have broad implications in biology, notably on the roles of CREs in development, evolution, and genetic disease.

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This thesis is not available in the repository or through interlibrary loan; to view it in person, visit the University Archives by telephone at 937-229-4256 or via email at archives@udayton.edu.


Undergraduate research



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