1. How do little elephants grow up to be BIG elephants?
How does a little elephant come to be?

2. CELL DIVISION!!

3. There are two types of cell division.
Mitosis – when an organism is growing, repairing or replacing cells
EX: skin cells replacing dead skin cells
Meiosis – when it’s time to reproduce an organism
EX: when you were created!

4. Meiosis or Mitosis? A) A snake sheds its skin.
B) My dog just had puppies.
C) You grew four inches in the last 2 years.

5. MITOSIS

6. Mitosis Cycle Interphase Prophase Metaphase Anaphase Telophase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

7. Interphase
The cell prepares to divide by copying its DNA

8. Interphase Plant Cell Animal Cell
Photographs from:

9. Prophase The chromatin in the nucleus condenses and forms chromosomes.
Centrioles appear at the poles of the cell.
The nuclear envelope breaks down.

10. Prophase Plant Cell Animal Cell
Photographs from:

11. Metaphase
The centrioles attach spindle fibers to the centers of each chromatid (a pair of chromosomes)
The chromatids are being pulled in both directions, so they end up lined up across the center of the cell.

12. Metaphase Plant Cell Animal Cell
Photographs from:

13. Anaphase 3rd step in Mitosis
The chromatids split up; half moving toward one pole and the other half moving toward the other pole.
The cell begins to stretch.

14. Anaphase Plant Cell Animal Cell
Photographs from:

15. Telophase Two new nuclear envelopes form.
The chromatids loosen up and appear as chromatin again

16. Cytokinesis
The cell membrane pinches into two ‘daughter cells’ that are exactly the same as the ‘parent cell.’

17. Animal Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

18. Plant Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

19. Cell Cycle

20. MEIOSIS

22. Meiosis Interphase
Meiosis is preceded by interphase. The chromosomes have not yet condensed.

23. Meiosis Interphase
The chromosomes have replicated, and the chromatin begins to condense.

24. Meiosis Prophase I
The chromosomes are completely condensed. In meiosis (unlike mitosis), the homologous (same) chromosomes pair with one another

25. Meiosis Metaphase I
The nuclear membrane dissolves and the chromosomes attach to the spindle fibers. They are preparing to go to opposite poles.

26. Meiosis Anaphase I The chromosomes move to opposite ends of the cell.

27. Meiosis Telophase I & Cytokinesis
The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes.

28. Meiosis Prophase II
The cell has divided into two daughter cells. These cells are diploid, they have a full set of chromosomes.

29. Meiosis Metaphase II
As in Meiosis I, the chromosomes line up on the spindle fibers.

30. Meiosis Anaphase II
The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell.

31. Telophase II & Cytokinesis
With the formation of four cells, meiosis is over. Each of these daughter cells have half the chromosomes of parent cells, which is called, haploid.

32. Meiosis is basically the same as mitosis, BUT it happens twice and it ends up with four cells at the end.
AND the four ‘daughter cells’ only have half of the chromosomes that the ‘parent cell’ had.

33. Mitosis Vs. Meiosis Mitosis Divides body cells
Same number of chromosomes as original cell (diploid)
The 2 daughter cells at the end will have 46 chromosomes (23 pair)
Meiosis
Divides sex cells
End up with ½ of the chromosomes of original cell (haploid)
The 4 daughter cells at the end will each have 23 chromosomes