2) Meiosis

• The formation of gametes involves meiosis.
• 1. Cell with two pairs of chromosomes (diploid cell).
  2. Each chromosome replicates itself.
  3. Chromosomes part company and move to opposite poles.
  4. Cell divides for the first time.
  5. Copies now separate and the second cell division takes place.
  6. Four haploid cells (gametes), each with half the number of chromosomes of the parent cell.
•  When a cell divides by meiosis:

  • copies of the genetic information are made
  • the cell divides twice to form four gametes, each with a single set of chromosomes
  • all gametes are genetically different from each other.
•  Meiosis is important because it halves the number of chromosomes in gametes.
• This means that fertilisation can restore the full number of chromosomes.