Graduation Year

2019

Date of Submission

12-2018

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Biochemistry

Reader 1

Findley Finseth

Reader 2

Kyle Jay

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Terms of Use for work posted in Scholarship@Claremont.

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2018 Silvia S Leblanc

Abstract

The inherent asymmetry of female meiosis presents an opportunity for genetic material to gain an evolutionary advantage during the formation of the egg. Since centromeres mediate chromosomal segregation by forming the bridge between microtubules and chromosomes during cell division, they are loci that can drive, or selfishly evolve, during female meiosis by manipulating the process of entering the egg. Mimulus guttatus, a species of yellow monkeyflowers, has the best documented case of centromeric drive (Fishman and Saunders, 2008). Since homozygotes for drive have decreased pollen viability, lower seed counts, and poor reproductive success, CENH3 —the gene that encodes the H3 histone specific to centromeres— has evolved to suppress centromeric drive. CENH3 is duplicated in Mimulus, and the sequence variation of CENH3_A suggests that this paralog can suppress centromeric drive during female meiosis (Finseth et al. 2015). Our analysis of gene expression levels in meiotic and mitotic tissues indicates that both CENH3_A and CENH3_B are still expressed at similar levels, suggesting that the paralogs have not specialized for different roles in cell divisions. However, qPCR was only performed with nine tissue samples, so further analysis of gene expression with a larger sample set is needed to confirm whether or not the CENH3 paralogs have specialized roles in meiosis and mitosis.

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