Meiosis

• What is meiosis?

  Cell division that results in four daughter cells, each with half the number of chromosones than the parent cells.

  During meiosis homologous pairs of chromosomes separate, so that once 1 chromosome from each pair enters a daughter cells. This is known as the haploid number of chromosomes
• Meiosis 1 - Prophase 1:

  • pairs of homologous chromosomes line up closely together
  • nuclear membrane breaks down
  • crossing over occurs, allows for exchange of material between non-sister chromatids
  • a chiasma ca randomly form creating a point of contact between chromatids
  • these are known as recombinants
• Meiosis 1 - Metaphase 1:

  • chromatids line up along the equator
  • random assortment: the random organisation of chromosomes at the centre of the cell
• Meiosis 1 - Anaphase 1:

  • spindle fibres contract and pull chromosomes apart
  • independant segregation: chromatids move to the other side
• Meiosis 1 - Telophase 1:

  • nuclear membrane reforms
  • cytokenisis occurs, resulting in 2 cells
• Meiosis 2 - Phrophase 2:

  • chromosomes condense and nuclear membrane breaks down
• Meiosis 2 - Metaphase 2:

  • chromosomes line up on the equator
• Meiosis 2 - Anaphase 2:

  • sister chromatids are pulled to the poles
• Meiosis 2 - Telophase 2:

  • cytokinesis occurs