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Presenter: David Bai

Faculty Sponsor: Tadasu Nozaki

School: UMass Amherst

Research Area: Genetics

Session: Poster Session 6, 4:15 PM - 5:00 PM, Concourse, B16

ABSTRACT

Diploid (2n) organisms contain two sets of homologous chromosomes, each of which must spatially pair during meiosis for crossover formation. In polyploid organisms (>2n), pairing becomes more complicated, as 3 or more homologous chromosomes must each pair during meiosis. The question of how these chromosomes pair and how polyploidy affects the progression of meiosis in vivo remains unsolved. To observe pairing in polyploid cells, budding yeast containing tagged fluorescent loci on chromosome II were prepared. Triploid (3n) and tetraploid (4n) yeast strains were constructed by disrupting the MATa or MATα locus and repeatedly mating. Ploidy level was then confirmed by flow cytometry and number of fluorescent spots. After meiotic induction, long timelapse live-cell imaging of the polyploids allowed for observation of chromosomal pairing during meiotic prophase I. The resulting imaging data showed that bivalent pairing occurs in the majority of cases, with trivalent and quadrivalent pairing being much less frequent. This suggests that chromosomes, once paired, employ a protective mechanism to prevent further pairing, even if there are still unpaired chromosomes in the nucleus.