Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 76-83).

Thesis (M.Med.Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 53-65).

No description available.

No description available.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Pathology / Master / Master of Medical Sciences

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Mitosis and meiosis are different forms of cell division. Mitosis is a non-reductive form of cell amplification whereby DNA chromosomes are replicated and segregated to form two progeny copies of the progenitor cell. Meiosis is a reductive form of cell division creating progeny containing half the chromosome copies of the progenitor cell. Improper chromosome segregation creates aneuploidy, which is poorly tolerated in cells. In cycling mitotic cells, aneuploidy leads to genome instability and cell death. Following meiosis, aneuploidy is associated with infertility, miscarriages, and birth defects. To segregate chromosome copies properly, pairs are physically organized and segregated to progeny cells by a mitotic spindle, whose functionality is tightly regulated. Kinesins are a family of highly conserved dimeric ATPase proteins which; organize spindle shape and size, facilitate chromosome capture and attachment to the spindle, and generate forces which are required for segregation. I investigated the molecular structure and function of human kinesin 13 family protein, Mitotic Centromere Associated Kinesin, MCAK. MCAK is a microtubule depolymerase whose full molecular structure and mechanism of depolymerization is not fully understood. Using in vitro biochemical assays and in vivo TIRF imaging, I found that altering MCAK molecular structure alters MCAK sub-spindle localization and by inference, alters global microtubule dynamics. This study suggests a potential mode for regulating of MCAK activity/function requiring further testing. Compared to over 30 kinesins in humans, showing a large amount of functional redundancy, yeast only has 6 identified kinesins whose function during meiotic cell division are still relatively unknown. I screened the importance and redundancy of yeast kinesins during meiosis. The results suggest similar roles and redundancies in meiosis to that during mitosis, despite different biochemical and biophysical spindle environments. Together, my investigations broaden the understanding of kinesin regulation and functional redundancy during different types of cell division.

Nanoscale biological systems operate in the presence of overwhelming viscous drag and thermal diffusion, thus invalidating the use of macroscopically oriented thinking to explain such systems. Rectified Brownian motion (RBM), in contrast, is a distinctly nanoscale approach that thrives in thermal environments. The thesis discusses both the foundations and applications of RBM, with an emphasis on nano-biology. Results from stochastic non-equilibrium steady state theory are used to motivate a compelling definition for RBM. It follows that RBM is distinct from both the so-called power stroke and Brownian ratchet approaches to nanoscale mechanisms. Several physical examples provide a concrete foundation for these theoretical arguments. Notably, the molecular motors kinesin and myosin V are proposed to function by means of a novel RBM mechanism: strain-induced bias amplification. The conclusion is reached that RBM is a versatile and robust approach to nanoscale biology.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 85-103).