FIGURE 3.

False color images of cell nuclei of stimulated human lymphocyte after thymidine treatment and BrdU incorporation. The DNA of the nuclei was counterstained with DAPI (a). Pericentric regions of chromosome X were labeled with rhodamine (b). Fluorescence labeling of the BrdU incorporation sites by FITC (c) indicated that from three-to-five nuclei were in S-phase for this image. In the merged image [(d) = (a)+(b)+(c)] the nuclei were classified as 1, G₀/G₁ cells, associated; 2 and 4, S-phase, associated X-centromeres; 3, S-phase, nonassociated X-centromeres; and 5, G₀/G₁-cells, nonassociated.