Student Theses and Dissertations

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

RU Laboratory

Zhao Laboratory


Phenotypic sex differences are essential byproducts and drivers of evolution in sexually reproducing species. Knowing how sex differences arise and how they influence evolution is central to our understanding of evolution. Although many facets of sex differences have been explored, many remain unknown. Here I focus on sex differences and the evolution of gene expression in three parts. First, I examine the evolutionary properties of genes with sex differences in mean expression levels in the Drosophila brain – a surprisingly understudied organ in this context. Second, I identify and characterize genes with sex differences in gene expression variability in human tissues – one of the first analyses of its kind. In both parts of the thesis, I focus on how the expression of genes with sex differences evolves. Finally, I step away from sex differences to investigate how chromatin accessibility evolves. Given the tight relationship between chromatin accessibility and gene expression regulation, this provides us with another window into the evolution of gene expression. In the first part, I show that sex-biased genes in the Drosophila brain are highly enriched on the X Chromosome. I show that X-linked male-biased genes, and to a lesser extent female biased genes, are enriched for signatures of directional selection at the gene expression level. By examining the evolutionary properties of gene-flanking regions on the X Chromosome, I find evidence that adaptive cis-regulatory changes are more likely to drive the expression evolution of X-linked male-biased genes than other X-linked genes. Finally, I examine how the shared genome between the sexes and expression breadth constrain the evolution of gene expression.


A Thesis Presented to the Faculty of The Rockefeller University in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy

Available for download on Friday, April 12, 2024

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