Meiotic and mitotic chromosomes from amphibians and snakes were studied by electron microscopy. By using water spreading, preceded by a mild NaCl pretreatment, we showed: 1. ‘Beads on a string’ arrangement of the chromatin fibres; 2. The presence of loops at pachytene chromomeres as well as during metaphase of both mitosis and first meiosis; 3. Transcriptional activity for non-ribosomal RNA on peripheral loops during the middle pachytene.
KeywordsMicroscopy Electron Microscopy Transcriptional Activity Mitotic Chromosome Lower Vertebrate
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