The spindle forms, chromosomes condense, the nuclear envelope fragments, the nucleolus disappears, homologous chromosomes pair off, and crossing-over occurs during

Answer: Prophase 1

Explanation:

Nuclear division is about to occur, nucleolus disappear, fragmentation of the nuclear envelope takes place.

The centrosomes apart from each other and the spindle fiber assembles.

Crossing over may take place at this time by the end of which the sister chromatids are no longer identical.

All of these events takes place during the prophase 1 stage of meiosis.