meiosis

• Meiosis


  The process that forms gametes (sex cells)
• Gametes


  Cells that only contain half the genetic material of a normal cell (haploid)
• Diploid cells


  Cells that have 23 pairs of chromosomes which are two sets of genetic information, one from each parent
• Meiosis


  1. Replication of DNA

  2. Chromosomes line up in pairs

  3. Chromosome pairs pulled apart

  4. Cell splits in two

  5. Pairs line up individually and are pulled to other ends of the cell.

  5. Cell splits in two again
• Chromosomes


  • Contain genetic information
  • Humans have 23 different types
  • Each type has two copies, one from each parent
• The left-to-right order of chromosome pairs is random during meiosis
• The DNA in each of the four gametes produced by meiosis is genetically unique
• Sperm and egg fuse during fertilization


  Form a diploid cell that can divide by mitosis
• The diploid cell can divide by mitosis to form an embryo, fetus, and fully grown organism
• Meiosis


  • This results in the formation of four genetically non-identical daughter cells.
  • Meiosis is used in sexual reproduction.
• 1. Cells split


  ,

  • Each cell has a pair of each chromosome (diploid cell).
  • During meiosis, each pair of chromosomes replicate and the cell splits in two.
• 2. Further cell splitting


  • There are now two identical cells.
  • The diploid cell divides again.
• 3. Haploid cells created


  • This creates four genetically different gametes that each have half the number of chromosomes of the parent cell. Cells that have only one copy of each chromosome (such as gametes) are called haploid cells.
• Meiosis is the formation of four non-identical cells from one cell.
• Meiosis (pmt)


  • The cell makes copies of its chromosomes, so it has double the amount of genetic information.
  • The cell divides into two cells, each with half the amount of chromosomes (46).
  • The cell divides again producing four cells, each with a quarter the amount of chromosomes (23).
  • These cells are called gametes and they are all genetically different from each other because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells.
• 4. Gametes fertilise


  • During sexual reproduction, the male gamete fertilises the female gamete and the fertilised cell now has the normal number of chromosomes (46 in humans).
• Mitosis


  • Once the gametes have combined, the new cell divides by mitosis (the cell grows asexually).
  • As soon as the embryo reaches a certain size, cells begin to differentiate (specialise).