Mitosis and meiosis

Mitosis and meiosis

Mitosis: cells divide in a series of stages called the cell cycle.
- Stage 1 – Interphase: cell growth, increase in number of organelles, DNA replicates so there are 2 copies of each chromosome (diploid).
- Stage 2 – Mitosis: one set of chromosomes is pulled to each end of the cell and the nucleus divides.
- Stage 3 – Cytokinesis: cytoplasm and cell membrane divide to form 2 identical daughter cells.
- Mitosis is important in the growth and development of multicellular organisms. It also replaces old or damaged cells.

Meiosis: cells in reproductive organs divide to form gametes, halving the number of chromosomes. Copies of the genetic information are made, and the cell divides twice to form four gametes, each with a single set of chromosomes.
- All gametes are genetically different from each other. They fuse at fertilisation, forming a zygote and restoring the full number of chromosomes.
- Meiosis leads to non-identical cells being formed.
- The zygote divides by mitosis, increasing the number of cells to form an embryo, and the cells differentiate as the embryo develops.

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