THE 3-DIMENSIONAL STUDY OF CHROMOSOMES AND UPSTREAM BINDING FACTOR-IMMUNOLABELED NUCLEOLAR ORGANIZER REGIONS DEMONSTRATES THEIR NONRANDOM SPATIAL ARRANGEMENT DURING MITOSIS

The volumic rearrangement of both chromosomes and immunolabeled upstre am binding factor in entire well-preserved mitotic cells was studied b y confocal microscopy. By using high-quality three-dimensional visuali zation and tomography, it was possible to investigate interactively th e volumic organization of chromosome sets and to focus on their intern al characteristics. More particularly, this study demonstrates the non random positioning of metaphase chromosomes bearing nucleolar organize r regions as revealed by their positive upstream binding factor immuno labeling. During the complex morphogenesis of the progeny nuclei from anaphase to late telophase, the equal partitioning of the nucleolar or ganizer regions is demonstrated by quantification, and their typical n onrandom central positioning within the chromosome sets is revealed.