NEET BIOLOGY

Detailed explanation-1: -During prophase, the nuclear envelope and nucleolus are dissolved and the chromosomes condense. The centrioles and spindle fibers begin to form at opposite poles of the cell. Chromatid separation is not seen until anaphase.

Detailed explanation-2: -During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down.

Detailed explanation-3: -The dissolving of the nuclear membrane is essential so the the chromosomes after separation to chromatids can travel to opposite ends of the parent cell. The new nucleus membranes than forms around them, enclosing them as two nuclei instead of one.

Detailed explanation-4: -In order for these processes to occur, the nuclear membrane must be dissolved during the earliest mitotic phase: prophase. During prophase, DNA condenses into chromosomes, the nuclear membrane dissolves, and the chromosomes enter the cytoplasm.

Detailed explanation-5: -During metaphase, the nuclear membrane disappears and the chromosomes become aligned half way between the centrioles. The centromere of each doubled chromosome becomes attached by thread-like spindle fibers to the centrioles which are at polar opposite sides of the cell.