AP BIOLOGY

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

Detailed explanation-2: -The disassembly of nuclear envelope is triggered by the cyclin-dependent kinase at the onset of mitosis. Phosphorylation of INM proteins disrupts their interaction with chromatin. Nuclear envelope breakdown is essential for sister chromatid segregation.

Detailed explanation-3: -1 DNA synthesis occurs at the beginning of prophase. 2 The nuclear envelope breaks down in prophase and reforms in telophase. 3 The division of centromeres occurs in anaphase.

Detailed explanation-4: -During prophase, chromatin condenses into chromosomes, and the nuclear envelope (the membrane surrounding the nucleus) breaks down. In animal cells, the centrioles near the nucleus begin to separate and move to opposite poles of the cell.