1. Cell Cycle, Mitosis

2. How do little elephants grow up to be BIG elephants?

3. Why do animals shed their skin?

4. The process of asexual reproduction begins after a sperm fertilizes an egg.

5. Three reasons why cells reproduce by asexual reproduction:
Growth
Repair
Replacement
Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cell that reproduce by asexual reproduction reproduce constantly.

6. Cells Multiply By Dividing
Eukaryotes:
Mitosis
Meiosis
Prokaryotes:
Prokaryotic (binary) fission

7. Mitosis is Nuclear Division
What is found in
the nucleus?

8. Chromosomes
Chromosomes - contain the genetic information (DNA) that is passed from parent to offspring.

9. 
Chromosomes
Chromosomes have two parts: chromatids held together by a centromere.
The chromatids are exact copies of each other and are split apart during mitosis to form single chromosomes.
Chromatids 
Centromere

10. Chromosome Replication
One chromatid 
Replication
sister
chromatids

11. 
When cells divide, sister chromatids separate so that each cell has the correct number of chromosomes.

12. 
46 … or … 23?
Diploid
Haploid
23 homologous pairs of (human) chromosomes (46 total, full number)
Somatic (body) cells (every cell except sperm and egg)
23 individual chromosomes (half the full number)
Gametes (Sex Cells: sperm and egg)

13. 
Human Chromosomes
Human diploid cells have 46 CHROMOSOMES – 2 COPIES OF 23 DIFFERENT CHROMOSOMES.

14. The Cell Cycle for Somatic Cells (p244-245)
The Cell Cycle for Somatic Cells (p )
2 Main Parts
Interphase (life, growth)
Mitosis (division of nucleus)
Consider cytokinesis (division of cytoplasm) as part of mitosis 2 1

15. Interphase Longer part of the cell cycle (90%) 3 Phases G1 (Gap)
S (Synthesis)
G2 (Growth)

16. During Interphase, DNA is relaxed and spread out thinly
During Interphase, DNA is relaxed and spread out thinly
Thin, stringy, “Invisible,” chromosomes are called CHROMATIN

17. The 3 Phases of Interphase
The 3 Phases of Interphase
G1 (Gap): Cell is living, doing normal processes
S (Synthesis): DNA replicates
G2 (Growth): Cell is expanding, replicating organelles, getting ready for division
No turning back after S phase starts! Cell will divide!

18. What happens after interphase?
MITOSIS

19. Cell Division  Mitosis is NUCLEAR division
Cytokinesis is CYTOPLASMIC division
We will call both (together) “Mitosis”

20. Check Point: Why Do Cells Divide?
Check Point: Why Do Cells Divide?
Growth
Repair
Reproduction
Mitosis
Meiosis

21. In Mitosis: diploid, somatic cells divide to become
In Mitosis: diploid, somatic cells divide to become
daughter cells
(mitosis makes exact copies of cells)
(*circle*) … diploid / haploid
(*circle*) … somatic / gamete

22. Mitosis Has 4 Main Phases Plus Cytokinesis (p246)
Mitosis Has 4 Main Phases Plus Cytokinesis (p246)
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
(With Cytokinesis)

23. Before we go any further, Let’s Learn Some Helpful Hand Signs!

24. PROPHASE

25. METAPHASE

26. ANAPHASE

27. TELOPHASE

28. Got It? Now we’ll talk about what happens in …M
Prophase
Metaphase A T
Anaphase
Telophase

29. TELOPHASE & CYTOKINESIS
Make A Table
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE & CYTOKINESIS
WHAT IT LOOKS LIKE
WHAT’S GOING ON

30. PROPHASE  Chromatin thickens into chromosomes
Centrioles
Chromatin thickens into chromosomes
Nuclear envelope disintegrates
Centrioles migrate to opposite poles
Centrioles begin producing spindle fibers

31. METAPHASE  Chromosomes line up along metaphase plate
Spindle fibers are made of microtubules
Spindle fibers attach at the centromere of duplicated chromosomes
Chromosomes line up along metaphase plate

32. 
ANAPHASE
Sister chromatids pulled apart to opposite poles

33. TELOPHASE & CYTOKINESIS
Nucleus reforms
Chromosomes begin to relax into chromatin (back to G1)
Cytoplasm splits to separate daughter cells

34. CYTOKINESIS (p248)  In Plant Cells In Animal Cells Cell Plate
Cleavage Furrow
(no cell wall)
Cell Plate
(to form cell wall)

35. What could happen if cytokinesis fails?

36. Can You Identify The Phases Of Mitosis?

37. Could you find the phases on a prepped slide?

38. Summary