Ultrastructure of the prophase kinetochore in cultured cells of rat-kangaroo (Potorous tridactylis)
Heneen, W.K.
Annales de Cardiologie et d'Angeiologie 24(1 Suppl): 209-220
1975
ISSN/ISBN: 0003-3928 PMID: 1137315 Document Number: 84489
Early prophase kinetochores in cultured cells of rat-kangaroo (Potorous tridactylis), cell line Pt-Kl, were recognizable at the earliest stages of chromatin condensation as patches of fine fibrillar material located in the vicinity of areas of highly condensed chromatin. These structures develop into a "ball-and-cup" appearance by mid- and late prophase. The diameter of the cup is 0.6- 0.8 μ. Kinetochore primordia occur in pairs, each primordium will be part of a future chromatid. The kinetochore is in linear continuity with the rest of the chromatid and occupies a large fraction of the chromatid's cross section. The chromatin continuity between the two proximal regions could reflect actual fibre continuity and/or fibre overlapping. The material of the kinetochore becomes finer and finer as it extends outwards with a consequent appearance of an "empty region" at the top of the cup. The organization of the mitotic kinetochore evidently progresses parallel with the process of chromatin condensation. A possible correlation between the fine structure of the prophase kinetochore and the light-microscopic descriptions given to this organelle is pointed out and discussed.