Fluorescence in situ hybridization (FISH) of chromosome spreads and interphase nuclei of lymphoblastoid cell of higher primates using probes specific to individual chromosomes. The figure illustrates the concept of chromosome territories with individual chromosomes occupying distinct spatial territories during interphase. Top row identifies chromosomes 16 (red) and 20 (green) in gorilla (a) and human (b). d shows selected z-slices of a marmoset interphase nucleus revealing the territories occupied by chromosome 18(red) and 19 (green). DNA is shown in blue.