How Does Meiosis Work?

Meiosis involves the chromosomes of parent cells breaking up to make copies of themselves, joining together to form new genetic material and chromosomes dividing to eventually form four gametes. This takes place over two phases; meiosis I and meiosis II.

During meiosis I:

  • Prophase I
  • Starting with a diploid cell, homologous chromosomes cross over genetic material. It is thanks to this that gametes achieve genetic diversity. The nuclear envelope then dissolves, allowing the centrioles to move towards the cell's pole and eventually attach to the chromosome's centromeres.

  • Metaphase I
  • Chromosome pairs align.

  • Anaphase I
  • Chromosomes move to opposite sides of the cell to reach the spindle fibers.

  • Telophase I
  • The cell's microtubules separate, allowing the cell to divide and form two more cells.

During meiosis II:

  • Prophase II
  • The nucleoli and nuclear envelope disappear, causing the centrioles to move to opposite sides of the cell.

  • Metaphase II
  • The chromatids realign along the cells center.

  • Anaphase II
  • Newly formed sister chromatids migrate to opposing sides of the cell.

  • Telophase II
  • During this final phase, the cells divide again, resulting in four gametes. This can mean four sperm or four oocytes (eggs).

As chromosomes divide and swap material during meiosis, each gamete is genetically diverse. When the gametes later come together to form a zygote, they result in further genetic diversity.