Mitosis

Interphase: new cell organelles are synthesised and DNA replication occurs. By the end of interphase, the cell contains enough cell contents to produce 2 new cells.

Prophase: the chromosomes condense, becoming shorter and thicker, with each chromosome visible as two strands called chromatids. Apart from the occasional mutation, the 2 strands are identical copies of one another, produced by replication. They're effectively two chromosomes joined at one region called the centromere. During prophase, microtubules from the cytoplasm form a 3D structure called the spindle. The centrioles move around the nuclear envelope and position themselves at opposite sides of the cell. These form the two poles of the spindle, and are involved in the organisation of the spindle fibres. The spindle fibres form between the poles. The widest part of the spindle fibre is called the equator.

Metaphase: the breakdown of the nuclear envelope signals the end of prophase and the start of metaphase. The chromosomes' centromeres attach to spindle fibres at the equator. When this has been completed the cell has reached the end of metaphase.

Anaphase: the centromeres split. The spindle fibres shorten, pulling the two halves of each centromere in opposite directions. One chromatid of each chromosome is pulled to each of the poles. Anaphase ends when the separated chromatids reach the poles and the spindle breaks down.

Telophase: effectively the reverse of prophase. The chromosomes unravel and the nuclear envelope reforms, so that the two sets of genetic information become enclosed in separate nuclei.

Cytoplasmic Division: in animal cells, the cell surface membrane constricts around the centre of the cell. A ring of protein filaments bound to the inside surface of the cell surface membrane is thought to contract until the cell is divided into 2 new cells. It has been proposed that the proteins actin and myosin, responsible for muscle contraction, may also be the proteins responsible for cytoplasmic division. Instead of undergoing this constriction, plant cells synthesise a new cell plate between the 2 new cells