Selfish genetic elements break the rules of Mendelian inheritance to bias their
transmission to following generations, often with negative fitness consequences. A striking
example involves selfish X chromosomes that operate in males and interfere with the
production of sperm that carry a Y chromosome. Only X chromosome-bearing sperm are
produced, and this can result in extraordinary female-biased sex-ratio distortions. Most
studies have focused on how selfish X chromosomes operate in and affect males, and there has been relatively little work on their consequences in females. In this thesis, I characterize fitness effects and transmission in females, in a recently discovered selfish X chromosome system in Drosophila testacea, a common woodland fly. I show that females with two copies of the selfish X chromosome have reduced fitness compared to females carrying zero, or one copy. Specifically, these females have a lower hatch rate and lifetime fecundity. Additionally, I show that heterozygous females are more likely to transmit the selfish X chromosome than the wildtype copy to their offspring. I observe this transmission bias in eggs, larvae, and adults, which suggests that the selfish X chromosome is preferentially segregating into the egg, rather than the polar bodies, during oogenesis. We believe this is the first documented case of a selfish X chromosome acting through both sexes. The negative fitness effects and the biased transmission in males and females will have important consequences on the evolutionary dynamics of the selfish X chromosome. In addition, the phenomenon of biased transmission in both sexes has the potential to yield interesting insights in the mechanism of meiotic drive. / Graduate / 2022-05-12
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/12998 |
| Date | 26 May 2021 |
| Creators | Powell, Candice |
| Contributors | Perlman, Steven John |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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