AP BIOLOGY

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

Detailed explanation-2: -During metaphase, the nuclear membrane disappears and the chromosomes become aligned half way between the centrioles.

Detailed explanation-3: -Final answer: ER and nucleolus begin to disappear during mitosis during late prophase.

Detailed explanation-4: -Telophase begins once the replicated, paired chromosomes have been separated and pulled to opposite sides, or poles, of the cell. During telophase, a nuclear membrane forms around each set of chromosomes to separate the nuclear DNA from the cytoplasm.

Detailed explanation-5: -The first and longest phase of mitosis is prophase. 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.