Defense Date

8-22-2013

Graduation Date

2013

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

Committee Chair

Michael I Jensen-Seaman

Committee Member

Philip E Auron

Committee Member

Brady Porter

Committee Member

Kateryna D Makova

Keywords

gene duplication, molecular evolution, primate, semen, sexual selection, sperm competition

Abstract

When asking the question of what underlying genetic changes drive species to be different, it is debated whether protein coding or non-coding mutations are more important. The hominoids (humans, great apes, and gibbons) are a group of closely related species, yet vary widely in their mating system behaviors and predicted levels of sperm competition. In species where females mate with multiple males, sperm competition is hypothesized to increase the rate of adaptive evolution of proteins expressed in male reproductive tissues through recurrent selective sweeps (positive selection). Previous studies have shown this to be true for individual male reproductive genes. In a comprehensive study of over six hundred proteins expressed in ejaculated semen, however, the same trend was not observed. Although, parsing the data based on their different functional and expression properties identifies a subset of proteins that are likely targets for adaptive evolution driven by sexual selection. Two of these rapidly evolving proteins are the duplicated, primate specific semenogelins, SEMG1 and SEMG2. An in vitro expression system was used to test if selection was acting similarly on the non-coding regions, but no effect of mating system on the expression was observed. However, the two genes are expressed differently within each hominoid species. One model for divergence after gene duplication is duplication-divergence-complementation. This model was used in conjunction with phylogenetic footprinting to identify potential regulatory elements that may be important for expression level differences between the two genes.

Format

PDF

Language

English

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