A nuclear envelope forms around each set of sister chromatids in

A nuclear envelope forms around each set of sister chromatids during telophase of mitosis and meiosis. Telophase is the final stage of cell division, following anaphase, and is characterized by the reformation of the nuclear envelope around the separated sets of chromosomes.

During telophase, the following events occur:

1. **Chromosomes Decondense**: The condensed chromosomes, which were present as distinct units during metaphase and anaphase, begin to decondense and revert to their extended, interphase state.

2. **Nuclear Envelope Reformation**: The nuclear envelope, which had disintegrated during prophase to allow for chromosome segregation, reforms around each set of separated chromosomes. This process involves the reassembly of nuclear pore complexes and the reintegration of nuclear membrane components.

3. **Nucleoli Reappear**: Nucleoli, which are regions within the nucleus where ribosomal RNA synthesis occurs, reappear as the nuclear envelope reforms.

4. **Cytokinesis Completes**: While telophase is occurring, cytokinesis, the physical division of the cytoplasm, also completes. In animal cells, this often involves the formation of a cleavage furrow, which constricts the cell membrane and eventually leads to the formation of two separate daughter cells.

Overall, telophase marks the conclusion of chromosome segregation and the beginning of nuclear reorganization as the cell prepares to enter interphase. The reformation of the nuclear envelope around each set of sister chromatids ensures the proper compartmentalization of genetic material within the newly formed daughter cells.