Chromosomes and Mitosis

• In order to survive and grow, our cells have got to be able to divide. And that means our DNA as well
• Chromosomes contain genetic information
• Most cells in your bodyhave 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 2 copies of each chromosome - one from the organism's 'mother', and one from the organism's 'father'
• Humans have 2 copies of chromosome 1 and 2 copies of chromosome 2, etc.
• There are usually 23 chromosomes in a human cell
• The cell cycle makes new 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 stage of 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 2 new daughter cells identical to the original cell, with the same number of chromosomes
• Growth & DNA replication - 1. 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 e.g mitochondria and ribosomes
• Growth & DNA replication - 2. 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 - Once its contents and DNA have been copied, the cell is ready for mitosis
• Mitosis - 4. The chromosomes line up at the centre of the cell and cell fibres pull them apart. These 2 arms of each chromosome go to opposite ends of the cell
• Mitosis - 5. Membranes from around each of the sets of chromosomes. These become the nuclei of the 2 new cells - the nucleus has divided
• Mitosis - 6. Lastly, the cytoplasm abd cell membrane divide. The cell has now produced 2 new daughter cells. The daughter cells contain exactly the same DNA - they're identical. Their DNA is also identical to the parent cell