Transgene sites visualized in nuclear halos from a tobacco plant line, which contains 60 transgene copies . A) DAPI staining, B) FISH signals clearly visible as two strings of dots. Nuclear halos were produced by treatment with LIS (lithium diiodo salicylate) which removes soluble proteins, including histones. The DNA can be seen as a halo surrounding a residual nucleus. In isolated nuclei, two signals, each corresponding to a homologous chromosome, are clearly visible (arrows). In contrast, in nuclear halos, a strand like arrow of signals is clearly visible. Bar, 10 μm.