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Subunit structure of chromosomes in mitotic nuclei of physarum polycephalum
Abstract:
We have investigated the subunit structure of mitotic chromosomes of the acellular slime mould Physarum polycephalum, using the nuclease susceptibility of isolated mitotic nuclei as a probe. A characteristic pattern of DNA digestion products is obtained, containing approximately integral multiples of a basic 140 base pair DNA segment that resembles very closely the pattern in G2 phase nuclei of Physarum and of calf lymphocyte nuclei. These results demonstrate that during the process of chromosome condensation there is no alteration at the primary level of chromatin structure that is responsible for the characteristic DNA digestion pattern.
Insights
Chromosomes in Physarum polycephalum maintain their basic DNA structure during condensation. Nuclease digestion reveals a consistent 140 base pair DNA segment, indicating no primary chromatin alteration during mitosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mitotic chromosomes undergo significant condensation during cell division.
- Understanding chromatin structure is crucial for comprehending chromosome dynamics.
Purpose of the Study:
- To investigate the subunit structure of mitotic chromosomes in Physarum polycephalum.
- To determine if chromosome condensation alters primary chromatin structure.
Main Methods:
- Isolated mitotic nuclei from Physarum polycephalum were used.
- Nuclease susceptibility assays were performed on the isolated nuclei.
- DNA digestion products were analyzed to identify characteristic patterns.
Main Results:
- A distinct DNA digestion pattern was observed, with fragments in integral multiples of a 140 base pair segment.
- This pattern closely resembled that of G2 phase nuclei in Physarum and calf lymphocytes.
- No alteration in the primary chromatin structure was detected during chromosome condensation.
Conclusions:
- The fundamental DNA organization within chromatin remains unchanged during chromosome condensation in Physarum polycephalum.
- The observed DNA digestion pattern is conserved across different cell cycle phases and species.
- Primary chromatin structure is not modified to facilitate chromosome condensation.