Meiosis

1
Meiosis

• Unit
• Cell Reproduction
• Biology

2
Meiosis

• Process of cell division that reduces the number
  of chromosomes to half
• Produces haploid cells called gametes
• Gametes are.
• Each gamete contains 23 chromosomes

Egg cell
Sperm cells
3
Meiosis

• One replication, two divisions
• Interphase I (G1, S, G2)
• chromosomes replicate to produce homologous
  pairs (sister chromatids)
• Meiosis I
• homologues separate
• Meiosis II
• sister chromatids separate

4
Meiosis I

• Interphase
• cell grows to mature size
• copies its DNA

5
Meiosis I

• Prophase I
• DNA coils tightly into chromosomes
• Spindle fibers appear
• Nucleus disappears

6
Meiosis I

• Metaphase I
• Tetrads line up in the middle
• They line up randomly with respect to the poles
  of the cell.

7
Meiosis I

• Anaphase I
• Each homologous chromosome (consisting of two
  chromatids) moves to opposite sides of the cell

8
Meiosis I

• Telophase I and Cytokinesis I
• Chromosomes reach opposite sides of cell
• Cytoplasm divides resulting in 2 cells

9
Meiosis II

• Prophase II
• DNA coils tightly into chromosomes
• Spindle fibers appear
• Nucleus disappears

10

• Metaphase II
• Chromosomes move to middle of each cell

Meiosis II
11

• Anaphase II
• Chromatids separate and move to opposite poles of
  each cell

Meiosis II
12

• Telophase II and Cytokinesis II
• A nuclear membrane forms around the chromosomes
  in each of the 4 cells
• DNA unwinds to chromatin form

Meiosis II
13

• Results in four new cells,
• Each cell contains half of the original cells
  number of chromosomes

Meiosis II
14

• A Comparison
• Mitosis
• And
• Meiosis