Chromosome dynamics required for successful meiosis, in particular, for meiotic homologous pairing. In sexually reproducing organisms, diploid germ cells produce haploid gametes (egg and sperm) by a specialized cell division process known as meiosis. During meiosis, chromosomes are segregated at two successive divisions without intervening DNA replication, reducing ploidy by half. In meiotic prophase, maternally and paternally-derived homologous chromosomes engage in crossover recombination events, resulting both in exchange of genetic material and formation of chiasmata that physically connect the homologs and ensure their segregation to opposite spindle poles at the first meiotic division. Prior to successful recombination, each chromosome locates, recognizes and associates with its homologous partner (homologous pairing) and then this association is stabilized by protein structure (synapsis). A failure in any of these steps can lead to chromosome rearrangement and/or non-disjunction, a leading cause of birth defects and miscarriages. Our laboratory is focusing on studying the chromosome dynamics required for successful meiosis, in particular, for meiotic homologous pairing. Although this process is essential for sexual reproduction, we are only beginning to understand its molecular mechanisms and many basic questions remain to be answered. How do chromosome move around in a nucleus in search for their homologous partner? How do chromosomes recognize their homology? How do chromosomes keep homologous association and/or discourage non-homologous association? How are initial association and stabilization (synapsis) coordinated? To address these fundamental questions, we use a simple model organism: the nematode C. elegans and employ a wide variety of techniques including functional genomics, genetics, molecular biology, cell biology and high-resolution 3-D microscopy.