Heterologous Segregations are established prior to chromosome congression in female meiosis I in Drosophila melanogaster.. Fiona M Lane, Ashley A Snouffer, William D Gilliland. Biological Sciences Department, DePaul University, Chicago, IL.

   Heterologous Segregation (HS) occurs in female meiosis when the genome is rearranged to carry multiple chromosomes that lack homologs. In those cases, the heterologous chromosomes will segregate away from each other at high frequency. While this phenomenon has been known since 1936, the mechanism to establish the co-segregation has remained unclear, as these chromosomes are not homologs, did not recombine, and do not pair with each other like normal homologous chromosomes. We propose that the recently-discovered process of chromosome congression in female meiosis establishes HS. We have examined different chromosome configurations that undergo HS, and show using chromosome-specific fluorescent in situ hybridization that the rates of coorientation at metaphase arrest match the rates of chromosome segregation observed in the progeny. Data will be presented that indicates when the coorientation must occur and indicates possible mechanisms for establishing these co-segregational configurations.