Mitosis and the cell cycle

• The nucleus of body cells contains chromosomes. In body cells the chromosomes are normally found in pairs. There are 46 chromosomes in human body cells. DNA is in the chromosomes and each chromosome carries a large number of genes.
• Cells divide so that organisms can grow during the development of multicellular organisms, and repair damaged tissues.
• Dividing cells go through a series of stages called the cell cycle. During the cell cycle the genetic material doubles and then divides to give two new cells that are genetically identical to each other and to the original cell.
• Before a cell can divide it must grow, and make copies of all the organelles such as mitochondria and ribosomes. It must also replicate the chromosomes in the nucleus. Then it can divide by mitosis.
• During mitosis, the two complete sets of chromosomes are pulled to opposite sides of the cell. Two new nuclei form. Then the cell splits into two.