prometaphase
"scientist have not discovered WHY it happens"It does not matter if scientists have discovered it or not, but the nuclear membrane disappears during PROPHASEHope this helped!!!
Prophase
In Prophase, the nuclear membrane disappears. In telophase, the nuclear membrane re-forms.
Disappears in prophase and reappears in telophase.
In the telo phase
Prophase
The phase of mitosis that begins when the nuclear membrane starts to fade is called prometaphase. During prometaphase, the nuclear membrane breaks down, allowing the spindle fibers to attach to the chromosomes.
The nuclear membrane reforms during late telophase of mitosis or meiosis, while the nucleolus reappears during interphase.
The phase where two new nuclear envelopes form around the two sets of daughter chromosomes is called telophase. In telophase, the nuclear membrane reforms around the chromosomes and the nucleoli reappear. This marks the end of nuclear division in cell mitosis.
During prometaphase, the nuclear envelope (membrane) breaks apart. However, some fragments of the nuclear envelope are still visible.
During prophase, the nuclear membrane and the nucleolus dissolve and disappear.
The phase where DNA is spread out as chromatin and the nuclear membrane is visible is the interphase. This is the period when the cell is not actively dividing, but preparing for division by duplicating its DNA and organelles.