Date of Award

Spring 2019

Document Type

Thesis

Terms of Use

© 2019 William N. Colgan. All rights reserved. This work is freely available courtesy of the author. It may only be used for non-commercial, educational, and research purposes. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Biology Department

First Advisor

Alexis Leanza, '15

Second Advisor

Bradley Justin Davidson

Abstract

Mutations to gene regulatory networks drive evolutionary adaptation, but mutations can also occur without phenotypic change. These neutral mutations instead lead to developmental systems drift, evolutionary divergence in developmental systems that does not alter the traits produced. Here we examine developmental systems drift between two tunicate species, Corella inflata and Ciona robusta, in the cardiopharyngeal gene regulatory network. Through cross-species assays and functional enhancer analysis, we assess the amount of drift both in cis and in trans. Here we show that the trans-regulatory architecture of the cardiopharyngeal gene regulatory network is largely conserved between C. robusta and C. inflata, but cis-regulatory elements within this network exhibit distinct levels of conservation. These results suggest that the amount of drift cis-regulatory elements undergo is not governed by overarching principles but rather by distinct structural and functional constraints which are unique to each cis-regulatory element. We show that the enhancer for FoxF, a key cardiopharyngeal gene, is highly conserved and propose a model for the unique structural and functional constraints which this cis-regulatory element experiences.

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