Between divisions, a copy of each chromosome is made. The chromosomes then start to become visible. The centrioles separate and move to opposite poles (ends) of the cell.
The chromosomes are clearly visible. They each consist of two threads called chromatids, each an exact copy of the parent chromosome. Chromatids are joined together at a point called the centromere.
The nuclear membrane disappears. The paired chromatids migrate to the middle line or equator, of the cell. From the centrioles, a system of fibres called the spindle stretches across the cell.
Each chromatid separates from its partner and they move to opposite poles of the cell (the spindle is thought to be involved in this). The chromatids are now considered to be daughter chromosomes.
Each half of the cell now has the correct number of chromosomes (six for this species). New nuclear membranes form around them and the cytoplasm starts to divide.
Cell division is complete. The chromosomes are no longer visible. Two daughter cells have been formed whose nuclei contain six chromosomes identical to the original six of the parent cell.
Genetic Terminology /