The DNA-based structure of human chromosome 5 in interphase.

In contrast to those of metaphase chromosomes, the shape, length, and architecture of human interphase chromosomes are not well understood. This is mainly due to technical problems in the visualization of interphase chromosomes in total and of their substructures. We analyzed the structure of chromosomes in interphase nuclei through use of high-resolution multicolor banding (MCB), which paints the total shape of chromosomes and creates a DNA-mediated, chromosome-region-specific, pseudocolored banding pattern at high resolution. A microdissection-derived human chromosome 5-specific MCB probe mixture was hybridized to human lymphocyte interphase nuclei harvested for routine chromosome analysis, as well as to interphase nuclei from HeLa cells arrested at different phases of the cell cycle. The length of the axis of interphase chromosome 5 was determined, and the shape and MCB pattern were compared with those of metaphase chromosomes. We show that, in lymphocytes, the length of the axis of interphase chromosome 5 is comparable to that of a metaphase chromosome at 600-band resolution. Consequently, the concept of chromosome condensation during mitosis has to be reassessed. In addition, chromosome 5 in interphase is not as straight as metaphase chromosomes, being bent and/or folded. The shape and banding pattern of interphase chromosome 5 of lymphocytes and HeLa cells are similar to those of the corresponding metaphase chromosomes at all stages of the cell cycle. The MCB pattern also allows the detection and characterization of chromosome aberrations. This may be of fundamental importance in establishing chromosome analyses in nondividing cells.