Laser Microsurgery on Chromosomes During Meiosis
James LaFountain Principal Investigator
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This project is to study the molecular mechanics of meiosis in the spermatocytes of crane-flies used as a model system. These are large, optically clear cells which have well formed chromosomes that make micromanipulations of the mitotic and meiotic structures relatively easy. This project focuses on meiotic events and contrasts these with the better-understood events of mitosis. The common assumption is that because the chromosome movements are so similar in both processes, the molecular mechanisms that give rise to these movements must also be similar. However, since some events are clearly unique to meiosis, such as the pairing of homologous chromosomes at the beginning of meiosis, some of the underlying molecular mechanisms may differ, at least in their details. The general approach will be to perform laser microsurgery experiments to ablate or disconnect various components of the chromosomes and spindle at different times during meiosis and to observe how these perturbations affect chromosome movements. Preliminary results suggest that chromosomes may be subjected to forces at their ends (telomeres) in addition to those forces generated at the sites where the chromosomes attach to the spindle (kinetochores). When previously paired chromosomes separate during meiosis, they behave as if their telomeres are tethered together. Objective 1 of this project will be to analyze this behavior in detail. Objective 2 is to study the detailed movements and reorientations of meiotic chromosomes as they congregate and pair prior to separation. The molecular mechanism of this congression is poorly understood, even in mitosis. As part of this objective, studies will be undertaken to determine if the rates of movement are load-independent (i.e. independent of the size of the chromosome). Objective 3 will expand the studies to other cells to determine if chromosome movements in spermatocytes are similar to those in other cells of the crane-fly and in cells of other species.