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Fig. 4. A colchicine-treated meristematic root-tip metaphase cell of a double
monotelosomic line of rye showing both the co-localization of the rDNA sites
detected by in situ hybridization (red) and the silver stained Ag-NORs (dark
brown). On condensed NORs (arrows), the silver signal reveals the previous
expression of rRNA genes, whereas the two hybridization sites of identical
size demonstrate that the two rDNA loci have equivalent numbers of ribosomal
cistrons. Bar, 5 µm.