Cell division and mitosis

• Most cells in your body have a nucleus. The nucleus contains your genetic material in the form of chromosomes
• Chromosomes are coiled up lengths of DNA molecules
• Each chromosome carries a large number of genes. Different genes control the development of different characteristics, e.g. hair colour
• Body cells normally have two copies of each chromosome - one from the organism's "mother" and one from its "father". So humans have two copies of chromosome 1, two copies of chromosome 2, etc.
• Body cells in multicellular organisms divide to produce new cells as a part of a series of stages caled the cell cycle
• The cell cycle when the cell divides is called mitosis
• Multicellular organisms use mitosis to grow or replace cells that have been damaged
• The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes
• In a cell that's not dividing, the DNA is all spread out in long strings
• Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
• After growing, it duplicates its DNA - so there's one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other
• Once its contents and DNA have been copied, the cell is ready for mitosis
• The chromosomes line up at the centre of the cell and the spindle fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
• Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided
• Lastly, the cytoplasm and cell membrane divide
• The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA - they're identical. Their DNA is also identical to the parent cell