Mitosis and Meiosis

1. Mitosis and Meiosis Why do we look similar to but different than our siblings?

2. Before mitosis OR meiosis… • Chromosomes duplicate (make a copy of themselves)

3. Mitosis • Fibers attach to chromosomes • Chromosomes line up along the middle of the cell • Chromosomes pulled to opposite ends of cell • New nuclear membranes form around chromosomes • Two new daughter cells are formed

4. Key points in mitosis • Two daughter cells are produced that are genetically identical to the original cell • A typical human cell has 46 chromosomes. How many chromosomes do the daughter cells have after mitosis? • Mitosis happens in the body for: • Growth • Repair • Replace old or damaged cells

5. Where does mitosis occur?

6. Cell division of reproductive cells • What would happen if the sperm and the egg were produced through mitosis? • This is why reproductive cells are created through a type of cell division called meiosis

7. Meiosis I • Pairs of duplicated chromosomes randomly line up along the middle of the cell • Duplicated chromosomes move away to opposite sides of cell

8. Meiosis II • Chromosomes line up along the center of the cell • Two strands of each chromosome separate and move to opposite ends

9. Results of meiosis • Four genetically different cells are produced • Each sex cell has HALF the number of chromosomes of the parent cell

10. Where does meiosis occur?

11. How does meiosis promote genetic variation? • Each cell has a different combination of chromosomes • Chromosomes can exchange genes during meiosis = new combinations • Each parent only contributes half of the chromosomes to offspring

12. Comparing mitosis and meiosis Similarities Differences