Visualization of metaphase chromosome equivalent accessibility in 2- and 3-dimensions. A. Epifluorescence image of metaphase cell hybridized with a low copy probe (3.4 kb) within NOMO1. 3D structured illumination microscopy of hybridized probe volume (panel B) and probe depth (panel C) for the homologs in panel A are presented. B. Both homologs show equivalent hybridization accessibility, where the fluorescence is embedded within the chromosome and protrudes above the surface. Reconstructed volume view in the left homolog was generated by up-righting it (arrow 1) and turning it clockwise about the z-axis (arrow 2) (see orientation schematic). Volume view in the right homolog was generated by up-righting it (arrow 1) and turning it counter-clockwise (arrow 2) (see schematic). C. Crosshairs are centered over the maximal fluorescent intensity projection along the XY, XZ and YZ axes for each chromosome 16 homolog. The axial projection (depth) of the probe fluorescence spans 15 of 18 0.1 μm reconstructed optical sections for both homologs, depicting equivalent chromatin accessibility (white rectangles delineate boundaries along the Z axis).