Assay of Chromosome Movement and Pairing During Meiosis in Saccharomyces cerevisiae Using Live Cell Imaging

James McGehee

Abstract

Meiosis is a specialized form of cell division, in which homologous chromosomes pair and form crossovers to ensure proper segregation. Improper segregation can lead to nondisjunction and diseases such as Down syndrome. It is not known if chromosome pairing is directed or stochastic, or whether chromosomes are held tightly together or allowed to dissociate. In this research, we assayed chromosome pairing in 3D space over time using Saccharomyces cerevisiae, with the goal of analyzing the role of actin and homology search with respect to chromosome motion and pairing during meiosis. Using homologous chromosomes tagged with Green Fluorescent Protein (GFP), we acquired images of yeast cells, and measured the distance between foci. We identified three classes of homolog interactions: always paired, never paired, and “kissing” where they pair and unpair. We calculated Mean Square Displacement (MSD) and the volume occupied by the foci to quantify chromosome motion. A shorter chromosome was tagged near the centromere, which exhibited active motion and a longer chromosome was tagged in the arm, which exhibited constrained diffusion.

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