Prophase
The phase where the nucleus and the nuclear membrane disappear is called prometaphase. This is the phase following prophase in mitosis or meiosis when the nuclear envelope breaks down and the chromosomes become more condensed and visible.
"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!!!
The nuclear membrane reforms and chromosomes disappear during the telophase phase of mitosis. In this phase, the separated sister chromatids reach the opposite poles of the cell, and the nuclear envelope begins to reassemble around each set of chromosomes. Subsequently, the chromosomes decondense back into chromatin, preparing for the next cell cycle.
The nuclear membrane fades during the prophase of mitosis or meiosis. This is the stage when the membrane begins to break down and disappear, allowing the chromosomes to become more condensed and accessible for cell division.
The phase of mitosis that the nucleus forms is the prophase phase.
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 second phase of mitosis is called prophase. During prophase, chromosomes condense and become visible as distinct structures. In addition, the nuclear membrane starts to break down, allowing the chromosomes to move freely within the cell.
telophase
The nuclear membrane reforms around the nucleus during Telophase, the last phase of mitosis.
The phase of mitosis where the nuclear envelope and nucleus disappear is called prophase. During prophase, the chromatin condenses into discrete chromosomes, and the spindle apparatus begins to form, facilitating the movement of chromosomes during cell division.
The longest phase of mitosis is typically prophase, as this stage involves the cell preparing for division by condensing its chromosomes, forming the mitotic spindle, and breaking down the nuclear membrane.
Spindles disappear during telophase, which is the final phase of mitosis. In this phase, the chromosomes reach the opposite poles of the cell, and the spindle fibers break down and disappear. This is followed by the reformation of the nuclear envelope around the separated sets of chromosomes, leading to the completion of cell division.