Chromosome Structure and Function during Meiosis Needhi Bhalla, Department of MCD Biology We are interested in the mechanisms that ensure that chromosomes segregate correctly during cell division, particularly in meiosis. During this specialized cell division, diploid cells give rise to haploid gametes, such as sperm and eggs, so that diploidy is restored by fertilization. Defects in meiosis can generate gametes, and therefore embryos, with the incorrect number of chromsomes. These aberrations in chromosome number, also referred to as aneuploidy, typically produce inviable embryos. It is estimated that 30% of human miscarriages are due to aneuploidy. In some cases, the presence of an extra copy of a chromosome can be tolerated by a human embryo but results in serious developmental disorders, such as Down and Klinefelters syndrome. Meiotic nuclei in the worm germline stained for proteins required for synapsis (red and blue) and recombination (green). We are specifically interested in how chromosome structure and function contribute to meiotic chromosome segregation. Early in meiosis, homologous chromosomes pair, synapse and recombine with their unique partner. All of these events are required for the proper segregation of chromosomes during meiosis. We combine genetic and biochemical approaches with high-resolution microscopy and cytological techniques to gain a more informed view of how molecular events during meiosis govern and are governed by higher-order chromosome behavior. We address these issues by investigating two processes in early meiosis: 1) how chromosomes monitor their own behavior during prophase and determine if they are synapsed and 2) how chromosomes are restructured around the recombination event to prepare for chromosome segregation. We perform most of our experiments in C. elegans, an organism that is amenable to genetic, cytological and biochemical manipulation