NEET BIOLOGY

Detailed explanation-1: -During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down.

Detailed explanation-2: -At the end of prophase I, the nuclear membrane breaks down, the centrosomes have migrated to the opposite ends of the cell, and the spindle apparatus is being formed. This is followed by metaphase I. During this stage, the spindle fibers, or microtubules, attach to the centromere of each chromosome.

Detailed explanation-3: -During prophase II, the nuclear envelope and nucleolus disappear. Spindle fibers stretch out from the centrosomes in all directions. The chromatin condenses and the chromosomes become visible under magnification. The sister chromatids are not identical, because of crossing-over during prophase I.

Detailed explanation-4: -During prophase II, chromosomes condense and the nuclear envelope breaks down, if needed.

Detailed explanation-5: -The nuclear envelope, including nuclear pore complexes, breaks down at the beginning of mitosis to accommodate the capture of massively condensed chromosomes by the spindle apparatus.