Date Approved

9-18-2024

Embargo Period

9-18-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.) in Molecular Cell Biology and Neuroscience

Department

Cell Biology and Neuroscience

College

Rowan-Virtua School of Translational Biomedical Engineering & Sciences

Advisor

Ronald Ellis. Ph.D.

Committee Member 1

Renee M. Demarest, Ph.D.

Committee Member 2

Michael Henry, Ph.D.

Committee Member 3

Dimitri Pestov, Ph.D.

Committee Member 4

Eric G. Moss, Ph.D.

Subject(s)

Evolutionary genetics; Nematodes

Disciplines

Genetics | Genetics and Genomics | Life Sciences

Abstract

In my research, I examined the characteristics of male and female sex-determination mutants in C. nigoni and investigated the regulatory pathway they define. This work tested whether flexibility in the sex-determination pathway was a preexisting condition that favored the origin of self-fertility in Caenorhabditis. Furthermore, I developed an approach for using interspecies hybrid mutants to assess the robustness of the C. nigoni pathway. My findings showed that the C. nigoni pathway is highly robust and canalized, suggesting that changes leading to self-fertility must have involved the impairment of this canalization in the germ line, to allow eventual alteration of germ cell fates in XX animals. I investigated how Haldane’s rule operates in nematodes by using C. nigoni and C. briggsae as models, employing mutant hybrids and tetraploids. I used sex-determination mutants to demonstrate that defects in XO hybrids were not due to incompatibility between regulatory programs specifying male fates. Instead, studies with tetraploids showed that mismatches between the X chromosome and autosomes in male hybrids are the key factor. Imbalances in gene expression are likely the result of genomic changes between these closely related species caused by rearrangements and by developmental system drift.

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