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Chromatin organization during meiotic prophase of Bombyx mori
Abstract:
Chromatin organization during the early stages of male meiotic prophase in Bombyx mori was investigated by electron microscopy. The analysis of nuclei prepared by the Miller spreading procedure, suggests that chromatin fibers which are 200-300 A in diameter undergo an orderly folding coincident with the formation of the synaptonemal complex. In very early stages the chromatin is released in linear arrays typical of interphase chromatin material. With time loops containing 5-25 mu of B conformation DNA, initially visualized at the periphery of early meiotic prophase nuclei, aggregate into discrete foci. These foci coalesce to form the longitudinal axis of the chromosome in conjunction with the initial appearance of the axial elements of the synaptonemal complex. At pachytene, the loops are evenly distributed along the length of the chromosome and extend radially so that in well spread preparations the chromosome has a brush-like appearance. Throughout this period nascent RNP-fibers were visualized along some of the loops.
Insights
Early male meiosis in Bombyx mori shows chromatin fibers organizing into loops. These loops aggregate, forming chromosome axes and synaptonemal complexes during prophase.
Area of Science:
- Cell Biology
- Genetics
- Microscopy
Background:
- Chromatin organization is crucial for meiosis.
- Understanding male meiotic prophase in Bombyx mori provides insights into chromosome dynamics.
Purpose of the Study:
- To investigate chromatin organization during early male meiotic prophase in Bombyx mori.
- To elucidate the relationship between chromatin folding and synaptonemal complex formation.
Main Methods:
- Electron microscopy was employed.
- Nuclei were prepared using the Miller spreading procedure.
Main Results:
- Chromatin fibers (200-300 A) fold orderly with synaptonemal complex formation.
- DNA loops (5-25 mu) aggregate into foci, forming chromosome longitudinal axes.
- At pachytene, chromosomes exhibit a brush-like appearance with radially extending loops and nascent RNP-fibers.
Conclusions:
- Chromatin undergoes significant reorganization during early male meiotic prophase.
- The formation of chromosome axes is closely linked to synaptonemal complex assembly.
- Distinct morphological changes in chromatin organization are observed throughout meiotic prophase stages.