Mitosis and meiosis

In short: In mitosis a cell divides into two genetically identical daughter cells, for example during growth. In meiosis germ cells with half the set of chromosomes arise.

In more detail: Mitosis serves growth and renewal. Meiosis ensures that at fertilisation the chromosome set becomes complete again.

In detail

• Phases of mitosis: Prophase, metaphase, anaphase, telophase. The chromosomes are duplicated and distributed.
• Meiosis: Two divisions in a row. Four different cells with a single chromosome set (23 in humans) result.
• Recombination: In meiosis chromosomes exchange segments. That shuffles the genes and creates variety.
• Errors: Distribution errors can change the chromosome number, for example in Down syndrome (trisomy 21).
• Cancer: Uncontrolled mitosis is a feature of tumours (dna-und-gene).