Honors Theses and Capstones

Date of Award

Spring 2020

Project Type

Senior Honors Thesis

Program or Major

Genetics

First Advisor

Kevin Culligan

Abstract

Epigenetics is the study of heritable changes that do not directly alter the DNA sequence. Many of these inheritance mechanisms are caused by the addition of a methyl group to cytosine nucleotides in DNA that prevent gene expression. The model organism Arabidopsis thaliana (abbreviated A. thaliana) is commonly used in genetic experiments, and its usefulness is extended to research in epigenetics. Our current research (Culligan lab), in part, focuses on genes involved in DNA damage and repair, such as brca2 and the rpa1a/b/c/d/e genes. Previous genetic analyses suggests that the rpa1c/e double-mutant typically expresses an early flowering phenotype despite no additional changes made to the nucleotide sequence or environment compared to other strains. One possible explanation to this phenomenon is the methylation of certain regions of DNA associated with flowering. The goal of this experiment is to identify epigenetic differences between the A. thaliana Col-O wild type and rpa1c, rpa1e and rpa1c/e mutants. From this research, different DNA methylation patterns could be identified in these rpa1 mutants, and the results could help researchers better understand how DNA methylation and histone modifications affect the development of an organism. Early flowering can also be seen in agricultural settings and can severely affect crop yields. Comparisons of growth between mutants showed significant differences between Col-O and rpa1e / rpa1c/e rosette leaf count and diameter. To test whether methylation patterns play a role in the early flowering phenotype, we employed an ELISA-based assay, which uses a standard curve of positive and negative controls, to determine methylation pattern differences in the WT and mutant lines. The standard curve for the ELISA assay was not adequate to use to compare the samples, possibly due to error while performing the assay, or issues with the controls.

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