Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Physics

First Advisor

Meredith Betterton

Abstract

Microtubules (MTs) are cytoskeletal polymers that assemble into a biomechanical complex known as the mitotic spindle. The spindle is responsible for the equal partitioning of chromosomes during cell division; an event known as mitosis. The dependence of proper chromosome segregation on the dynamics of individual microtubules (MTs) is not well understood or easy to study due to their small size and quick dynamics. Mathematical models and simulations have been constructed in order to better understand the physical basis of how the mitotic spindle accurately, or inaccurately, divides duplicated chromosomes during mitosis. These models rely on the dynamics parameters of individual MTs, some of which are difficult to measure due to the resolution limits of live cell microscopy. This research has better quantified the dynamics of mitotic MTs in an effort to further restrict parameter ranges implemented in simulations of mitosis. Using biological and computational methods, I created a microscopy protocol to image fission yeast cells stalled in early mitosis and developed a pipeline that allows for the direct analysis of MT dynamics from raw micrograph data. I also conducted various bleaching experiments to determine kinetics of unresolvable MTs during spindle formation. I developed a kinetic Monte Carlo simulation of the stalled mitotic spindle that can be used to generate simulated data to benchmark the performance of the analysis techniques. This work has better defined parameter ranges for the dynamics of mitotic microtubules, values critical for accurate simulation of chromosome segregation, as well as developed a computational pipeline that may be applicable to a wide range of other biological microscopy data.

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