3.24c mitosis

Key points:
The nucleus of the cell contains chromosomes. During the resting stage of the cell cycle known as the interphase, the chromosomes undergo a process called DNA replication. This creates two copies of each chromosomes which are held together by a structure called the central mere.

Normally, you would see the nucleus as a spherical structure and you would not be able to see any chromosomes. The first sign that a cell is going into mitosis is when you see the nucleus membrane breaking down. Called pro phase. Then the chromosomes become visible. Visible as a pair of Chromatids. Each chromosome has been copied, held together by central mere. The cell division continues, inside the cell a network of protein molecules, spindle and the spindle fibres, extend from one pole of the cell to the other. Late pro phase, chromosome pair will move towards the spindle and will join to one spindle fibre at the central mere. Next stage, metaphase. To show it easily, its only showing one pair of chromatids. The pair of chromatids join on the spindle fibre at the equator, or middle of the fibre. The next phase is known as the Anaphase. In the anaphase, the spindle fibre shortens and pulls the chomatids in opposing direction. They separate and move to the poles of the cell. The end of mitosis is shown by telophase, in which the nucleus begins to reform around the chromosomes which have been pulled to the poles of the cell. So in the telophase we see the formation of 2 nuclei at opposite ends of the cell. Finally, a phase known as cytokinesis, the cell splits into two. This is NOT part of mitosis. The cell divides itself, and the membrane will fuse across the middle. They each contain a chromosome which is the same as the parental chromosome. Basically, both cells each contain the same amount of chromosomes as the parent cell, eg. if the parent cell had 23 chromosomes, then both of the cells created would EACH have 23 chromosomes.