Graduation Year

2026

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Molecular Biology

Reader 1

Findley Finseth

Reader 2

Kyle Jay

Abstract

Selfish genetic elements such as meiotic drivers bias their own transmission, challenging Mendelian inheritance and shaping genome evolution, often at a cost to organismal fitness. Understanding the genetic basis of these trade-offs is essential for explaining how drive systems persist in natural populations. Female meiotic drive in Mimulus guttatus biases allele transmission through an expanded centromere on chromosome 11 and is associated with reproductive fitness costs. NASP, a CenH3 chaperone located within the MDL11 region, is a strong candidate gene for mediating these costs. This project, expanding upon the work of Amelia Douglass (2025), tests whether sequence variation between drive (D) and non-drive (D−) NASP alleles contributes to reproductive fitness differences. M. guttatus NASP alleles were expressed in Arabidopsis thaliana nasp mutants, via a T-DNA transgenic complementation approach; then, effects on male and female fertility were quantified through pollen viability, seed set, and silique length. Across experiments, no consistent or statistically significant differences in fertility were detected between genotypes, and control lines did not behave as predicted. While some trends were observed in individual datasets, these patterns were not reproducible across experiments. These results suggest that allele-specific effects of NASP, if present, may be subtle or dependent on genetic and experimental context. Additionally, variability across datasets highlights potential limitations of the transgenic system, including overexpression and incomplete genotype validation. Taken together, these findings do not provide strong evidence for a direct role of NASP allele variation in reproductive fitness in this system, but remain consistent with the possibility that NASP contributes to drive-associated fitness costs in a context-dependent manner. Further validation and analysis, particularly in native genomic backgrounds, will be necessary to clarify NASP’s role in the molecular mechanisms underlying meiotic drive in Mimulus guttatus.

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Available for download on Sunday, April 30, 2028

This thesis is restricted to the Claremont Colleges current faculty, students, and staff.

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