Final answer:
During prophase of mitosis, several events occur, such as the breakdown of the nuclear envelope and the movement of centrioles in animal cells. Centrioles are organelles that ensure each new cell formed after cell division contains a complete set of chromosomes.
Step-by-step explanation:
During prophase of mitosis, several events occur. The nuclear envelope starts to break into small vesicles, the Golgi apparatus and endoplasmic reticulum fragment and disperse, and the nucleolus disappears. The centrosomes move to opposite poles of the cell, and microtubules form the mitotic spindle.
The sister chromatids start to coil tightly and become visible under a microscope. In animal cells, centrioles near the nucleus begin to separate and move to opposite poles of the cell. Centrioles are organelles that ensure each new cell formed after cell division contains a complete set of chromosomes.