Kinetochores on chromosomes enclosed within the nuclear envelope.

The kinetochore plate which develops after nuclear envelope breakdown in normal cells can be seen to be formed on condensed chromosomes still enclosed in the nuclear envelope in fused multinucleate cells where some nuclei show delayed envelope breakdown caused by nuclear interaction. This suggests that neither nuclear envelope breakdown nor assembly of microtubules is directly related to the formation of the kinetochore plate. Furthermore, it can be clearly observed in these cells that the kinetochores do not have any special association with the nuclear envelope.