Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science in Biology

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Pinto, Ines

Committee Member/Reader

Evans, Timothy

Committee Member/Second Reader

Herold, Warren

Committee Member/Third Reader

Dowdle, Andrew

Abstract

Errors in chromosome segregation during cell replication are detrimental to the health of living cells. These errors cause aneuploidy: daughter cells with an incorrect number of chromosomes, as well as polyploidy: the complete duplication of a genome. In humans, these segregation errors are responsible for many harmful diseases and disorders. Using the model organism S. cerevisiae, a double mutant was created by removing two key chromosome remodeling complexes, SWR1 and INO80, both known to independently cause aneuploidy, decreased fitness, and damages the sensitivity of a cell's DNA (Andalis et al. 2004). By creating a double mutant strain, genetic cell ploidy was analyzed after several generations of growth to identify the effects of removing both complexes. To further investigate possible mechanical sources of aneuploidy during mitosis, chromosome centromeres and microtubules were tagged with fluorescent proteins to track and follow the movement of centrosome during cell division. After twelve passages of continuous growth for each yeast strain, cell ploidy was analyzed using flow cytometry. It was found that the removal of either the SWR1 or INO80 complexes in haploid cells led to diploidy after various generations. SWR1 began displaying diploidy by the sixth passage while the INO80 showed diploidy by the first passage and appeared to have stabilized in the diploid form by the twelfth passage. The double mutants carrying deletions of both complexes displayed results like that of a single deletion of INO80 and stabilized in diploidy slightly quicker than the INO80 single mutant. The centromere tag was then tracked using fluorescent microscopy and found that the mutant strains that had diploidized contained two copies of the signal, indicating the duplication of that chromosome, consistent with the diploid DNA content seen by flow cytometry.

Keywords

S. cerevisiae, genetics, yeast cell ploidy, Benomyl Sensitivity, Fluorescent Microscopy, Flow Cytometry

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