Figure 1. [Figure is also reproduced in color section.] Visualizing human chromosome 13 by fluorescence in situ hybridization (FISH). Two-dimensional preparations of 3:1 methanol:acetic acid fixed nuclei were hybridized with biotinylated chromosome 13 paint and detected with fluorochrome-labeled antibodies (green). DNA is counterstained with 4¢,6-diamidino-2-phenylindole (DAPI) (blue). Two distinct territories are visible in the interphase nucleus, chromosome 13 is gene-poor and hence peripheral (Croft et al., 1999).

Figure 2. Fluorescent labeling of whole chromosomes in living cells. Proliferating cells are grown in medium supplemented with fluorescently tagged nucleotides (a). On completion of S phase, each newly replicated chromatid is labeled (b). Further cell divisions in normal medium allow random segregation of the labeled chromatids through the daughter cell population (c). Several cell divisions later, cells will have, on average, only one or two fluorescently tagged chromosomes (d). (From Zink D, et al. 1998).

Figure 3. [Figure is also reproduced in color section.] Visualization of the distribution of CpG islands in the human genome by fluorescence in situ hybridization (FISH). Male metaphase chromosomes hybridized with a pool of DNA that represents CpG islands (red) allow the distribution of these gene markers to be studied. Gene (CpG) island rich chromosomes include 17, 19 and 22. BrdU (green) was incorporated into late-replicating DNA to visualize G bands. The figure shows that most gene/CpG island dense regions are in bands with no BrdU staining, i.e. in early-replicating R and T bands. (Adapted from Craig JM and Bickmore WA 1994).