The nuclear membrane dissolves during prometaphase, a stage in mitosis. This disassembly of the nuclear envelope allows sister chromatids to be released from the nucleus for separation into daughter cells. The process involves fragmentation of the nuclear membranes into vesicles, disassembly of nuclear pore complexes, and depolymerization of the nuclear lamina through phosphorylation by specific kinases such as Cdc2 protein kinase. The nuclear membrane breakdown begins near the end of prophase and is completed in prometaphase, facilitating chromosome segregation during mitosis.
