Mitosis and meisos

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  • Mitosis + Meiosis
    • Mitosis
      • Cell division that makes animal and plants grow
      • How old and damaged cells are replaced
      • A Parent Cell divides into 2 identical daughter cells
      • 1. Chromosomes are found in the nucleus
        • 2. Chromosomes duplicate to chromatids- long and thin
          • 3. Chromatids condense, join together at centromere
            • 4. Spindle fibres (proteins) stretch from each side of the cell and attach to the centromere. Arranges chromatids in the centre of the cell
              • 5. Spindle fibres contract, pulling the 2 chromatids apart. Nuclear envelope reforms around each set and the cell starts dividing
                • 6. Cell finishes dividing in 2 and the chromosomes become longer and thinner.
      • Produces DIPLOIDS -46 chromosomes
    • Meiosis
      • Gametes are produced
      • Half the number of chromosomes (reduction division)
      • Produces 4 unique daughter cells
      • Ensures natural variation within a species
        • Small parts of homologous chromosomes cross over, this exchange of genetic material increases variation
      • 1st round of division- Homologous pairs of chromosomes align in the middle of the parent cell and separate
        • The cell divides so each new daughter cell only contains 1 chromosome from each pair (23 in total)
          • 2nd round- In each cell, the chromosomes align at the centre + its chromatids pulled apart into separate halves of the cell
            • Each cell divides again, so each cell only contains 1 chromatid form each chromosome


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