Chromosomes and mitosis

• Chromosomes contain genetic information
• 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
• Body cells normally have two copies of each chromosome - one from the organism's mother and one from its father. So, human's have two copies of each chromosome.
• Each person has 23 pairs of chromosomes
• The cell cycle makes cells for growth, development and repair
• Body cells in multicellular organisms divide to produce new cells as part of a series of stages called the cell cycle
• The stages of the cell cycle when the cell divides is called mitosis
• Multicellular organisms use mitosis to grow and develop or replace cells that have been damaged.
• The end of the cell cycle results in two cells identical to the original cell, with the same number of chromosomes
• 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 copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
• Mitosis:

  • The chromosomes line up at the centre if 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 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.