DNA replication in Physarum polycephalum. Analysis of replicating nuclear DNA using the electron microscope

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Understanding DNA replication mechanisms is crucial for cell division.
• Physarum polycephalum offers a unique model for studying the cell cycle.

Purpose of the Study:

• To investigate the structure of replicating DNA in Physarum polycephalum.
• To identify and characterize putative DNA replication origins.

Main Methods:

• Isolation of DNA from Physarum polycephalum nuclei at various mitotic stages.
• Electron microscopy for visualizing DNA structures.
• Analysis of DNA segments and replication clusters.

Main Results:

• Identified 'microbubble' clusters within replicating DNA structures.
• Each microbubble represents DNA segments of 100-5000 nucleotides.
• Replicating segments (clusters) averaged 16400 nucleotides, separated by non-replicated regions.

Conclusions:

• Microbubble clusters may represent functional replicons in Physarum DNA.
• Multiple initiation sites for DNA synthesis are suggested within these replicons during S-phase.