Fig. 5. DNA decondensation in transcriptionally active loci. Endosperm nuclei of line E were hybridized with probes for pHMW-1Ax1 and pHMW-1Dx5, detecting the whole plasmids (green, A) or with probes detecting the flanking sequences and the vector (green, B) and counterstained with DAPI (blue). Overlay of several confocal sections showing only one of the three loci per nucleus. An overlay of all optical sections through the nucleus is shown for the DAPI staining in A and B to illustrate the similar sizes of the two nuclei. (A) Condensed locus at 6 dpa before the start of expression. (B) Transcriptionally active locus at 16 dpa in a rarely seen linear conformation. In the straightened chromatin fibres, the complex structure of the locus, which is broken up by genomic sequences, becomes visible. Bar, 10 µm; section spacing is 0.4-0.6 µm.