1. Welcome to the World of Cell Division
Mitosis

2. Mitosis
One splits into two identical daughter cells

3. Chromosomes
All chromosomes are made of D.N.A. or deoxyribonucleic acid
D.N.A. is a blueprint for the cell
D.N.A. stores and passes on all the genetic material from one generation to the next
D.N.A. was discovered by two scientists—James Watson, an American, and Francis Crick, a Brit

4. Structure of Chromosomes
Nucleus
ANY plant or animal cell

5. Structure of D.N.A. Adenine Thymine Cytosine Guanine
Double Helix (like a spiral staircase)
The sides of the ladder are made of sugar and phosphate groups
The rungs of the ladder are made up of a pair of nitrogen bases:
Adenine
Cytosine
Guanine
Thymine
Adenine Thymine
Cytosine Guanine

6. Rosalind Franklin
It was Franklin's photographic skills that made the discovery of D.N.A. possible.
Photo showed the double-helix shape.
Watson said, "My jaw fell open and my pulse began to race!"
…behind closed doors he also was quoted, “She’s frumpy…”

7. Mitosis Cell Division occurs in a series of stages
We will look at six stages of mitosis:
Interphase
DNA Replication
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

8. Interphase
This is the phase of a cell’s life when it is not undergoing mitosis (10-14 hrs). There are two parts: D.N.A. Replication and Growth and development
At the beginning of interphase:
Chromosomes are threadlike and called chromatin
Centrioles are located outside the nucleus in animal cells
At the end of interphase:
Chromosomes duplicate
Sister Chromatids (products of duplication) are connected at centromere
Cell increases in size and the organelles duplicate

9. Interphase

10. D.N.A. Replication

11. D.N.A. Replication 1.

12. D.N.A. Replication 2.

13. D.N.A. Replication 3.

14. D.N.A. Replication 4.

15. DNA Replication 1. The double helix uncurls.
2. DNA unzips along the nitrogen bases
3. Free nitrogen bases in the nucleus match up with their pair.
4. Sides of the ladder reform. Now there are two identical copies of D.N.A. molecules (the sisters).

16. Prophase Centrioles move to opposite sides of the cell
Spindle fibers form between centrioles
Nuclear Membrane breaks down
Nucleolus disappears

17. Prophase C C

18. Metaphase Chromosomes attach to the spindle fibers at the centromere
Chromosomes line up along the equator of the cell

19. Anaphase Sister chromatids separate
Chromosomes move to opposite ends of the cell being pulled along by the spindle fibers

20. Telophase Cytokinesis
Chromosomes uncoil and lose their rod-like appearance
Nuclear membrane reforms around each pair of chromosomes
Nucleolus returns
(In animal cells) The cell membrane around the cell moves inward, pinching the cell into 2 equal parts.
(In plant cells) Vesicles fuse together to form a cell plate which then fuses with the cell membrane
Cell membrane forms two identical daughter cells

21. Human Skin Cell Cycle