The three main stages of the cell cycle are:
– Interphase – The period before cell division occurs. During interphase, the cell grows to its mature size, makes a copy of its DNA, and prepares to divide into two cells.
– Mitosis – The stage during which the cell’s nucleus divides into two new nuclei. During mitosis, one copy of the DNA is distributed into each of the two daughter cells.
– Cytokinesis – This process completes the process of cell division. During cytokinesis, the cytoplasm divides, distributing the organelles into each of the two new cells.
DNA in a cell must replicate before the cell divides because DNA carries out all the information a cell needs to function. As a cell must have a complete set of DNA to survive, it is highly important that DNA must replicate before the cell divides.
In a plant cell, a rigid cell wall cannot squeeze together in the same way that a cell membrane can. A cell membrane in an animal cell, however, squeezes together around the middle of the cell.
If the centromeres did not split and the chromatids did not separate during anaphase, the cell would not become stretched. Also, the cell would be unable to go onto the next stage of mitosis, telophase, in which the chromosomes begin to stretch out and lose their rod-like appearance. The cell would remain as one, and be unable to split.