1. Chapter 3.5
Cell Division

2. Bell Ringer A small baby snake grows into a larger adult snake.
How does this happen?
Explain your thinking.

3. How do organisms grow?
Brainstorm with your partner

4. How do organisms grow?
In size
In number

5. The Cell Cycle
Cells grow and divide to make identical cells.
Why?

6. The Cell Cycle Cells grow and divide to make identical cells. Why?
To reproduce (unicellular organism)
To grow or repair tissue (multicellular organism)

7. The Cell Cycle Goal: Grow and Divide
Stages: Interphase, Mitosis, Cytokinesis

8. Interphase Cell grows, doubles its DNA and prepares to divide.
Activities occur in 3 phases:
Cell grows organelles in G1 phase
DNA is copied in S phase
Centriole doubles in G2
(only animal cell have centrioles)

9. G1 phase Longest phase of the cell cycle.
Cell does its job for the body.
Cell grows bigger.
Makes more organelles.

10. S phase DNA is doubled by DNA replication.
DNA replication takes several hours.

11. DNA Structure and Replication
DNA structure is key to its ability to make identical copies of itself. Why?
DNA Structure
made of 4 building blocks
called nucleotides
adenine
thymine
guanine
cytosine
Nucleotides pair up: (A-T) (C-G)

12. Your Turn: Identify the nucleotides on the second DNA strand
Write in the sequence by yourself.
Then, check your answer with your partner.

13. Your Turn: Identify the nucleotides on the second DNA strand

14. DNA Structure and Replication
DNA replication ensures each daughter cell will have all the same genes as the parent cell.
Remember:
Nucleotides always pair up
(A-T) (C-G)
With your partner:
Explain how DNA structure makes it easy to make identical copies.

15. G2 phase Final preparations for cell division are made.
In animal cells: centrioles double

16. Mitosis The cell’s DNA is carefully divided into two nuclei.
Each new nucleus gets a complete set of DNA.

17. DNA coils so it can be carefully moved
Chromatin coils into a chromosome

18. Chromosome Parts

19. PMAT (stages of mitosis)
Mitosis controls the movement of chromosomes
Centrioles move to opposite ends.
DNA chromatin coils into chromosomes.
Identical chromosomes PAIR UP.
Spindle fibers attach to chromosomes.
Chromosome pairs move to the MIDDLE.
Chromosomes pairs are pulled APART.
TWO nuclei form.

20. Cytokinesis in Animal Cells
Division of the cytoplasm.
Two new identical cells form.

21. Cytokinesis in Plant Cells
Division of the cytoplasm.
Golgi vesicles fuse into cell plate.
Cell plate extends and becomes the cell wall.
Two new identical cells form.

22. Daughter Cells
Will daughter cells have the same number of chromosomes as the original parent cell?
Why? Discuss with your partner.

23. Review: The Cell Cycle
Goal:
Activities at Each Stage:

24. Why do we care about the cell cycle?
Any ideas?
Think about our bodies, our growth, our health… brainstorm with your partner.
Normal Cell Cycle

25. Why do we care about the cell cycle?
Normal Cell Cycle
Uncontrolled Cell Cycle
Increased Growth

26. Cancer is a disease of the cell cycle
Uncontrolled cell division and cell growth leads to tumors.

27. Normal vs. Cancer Cells
What makes the cells look different?

28. If scientists can explain how the cell cycle works and is regulated will they be able to intervene and stop cancer?
8 min