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Surface structure of isolated metaphase chromosomes
Experimental Cell Research
|August 1, 1983
Summary
Scanning electron microscopy revealed that mitotic chromosome surface protuberances in HeLa cells depend on magnesium ion concentration. Lower Mg2+ levels cause fiber expansion and a knobby surface, suggesting radial fiber arrangement.
Area of Science:
- Cell Biology
- Molecular Biology
- Biophysics
Background:
- Mitotic chromosomes exhibit complex structures crucial for cell division.
- Understanding chromosome surface morphology and fiber organization is key to elucidating their function.
Purpose of the Study:
- To investigate the relationship between surface protuberances of mitotic chromosomes and their underlying fiber organization.
- To determine the effect of varying magnesium ion (Mg2+) concentrations on chromosome structure.
Main Methods:
- Scanning electron microscopy (SEM) was employed to visualize isolated HeLa cell mitotic chromosomes.
- Chromosomes were prepared using a method that avoids organic solvents and extreme pH conditions.
- Experiments were conducted across a range of Mg2+ concentrations (5.0 mM down to 0.05 mM).
Main Results:
- At 5.0 mM Mg2+, chromosomes displayed a condensed structure with a smooth surface.
- Decreasing Mg2+ concentrations (1.5 mM to 0.05 mM) revealed a knobby surface substructure with increasing protuberance diameters.
- At low Mg2+ concentrations (0.05 mM), chromosomes expanded, highlighting the underlying fiber organization and suggesting a radial looping of fibers.
Conclusions:
- Chromosome surface protuberances are significantly influenced by Mg2+ concentration.
- The observed knobby surface morphology likely results from a radial arrangement of chromosomal fibers.
- This study provides insights into the structural organization of mitotic chromosomes at the nanoscale.