Chromosones and Mitosis

• To survive and grow, our cells have to be able to divide.
• Chromosomes contain genetic information

  • Most cells in your body have a nucleus (that 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 the 'father'
• Human body cells have 46 chromosones.
• Human body cells have 23 pairs of chromosones.
• The cell cycle makes cells for growth, development, and repair.

  • Body cells in multicellular organisms divide to produce new cells as a part of a series of stages called the cell cycle.
  • The stage of the 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 chromosones.
• There are two main stages of the cell cycles

  • Growth and DNA replication
  • Mitosis
• Growth and DNA replication

  • 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.
  • It then duplicates its DNA- so there's one copy for each new cell. The DNA is coped and forms X-shaped chromosomes. Each arm of the chromosome is and exact duplicate of the other.
• Mitosis

  • Once a cells contents and DNA have been copied it can perform mitosis
  • The chromosomes line up at the center of the cell and cell 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 been divided.
  • The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA- they're identical to each other and the parent cell.
• If the body fails to control when cells divide it can result in cancer.