1. Unit 3: Biology Lesson 4: Cell Cycle and Cell Division
Science 9H
Unit 3: Biology
Lesson 4: Cell Cycle and Cell Division

2. Objectives By the end of the lesson you should be able to:
Describe the 5 stages in the cell cycle
Describe the 4 steps in mitosis

3. Cell Division Rates Cells divide at different rates:
Brain cells: every days
RBC: every 120 days
Skin cells: every 20 days
Liver cells: every 200 days
Stomach lining: every 2 days!
Intestinal lining: every 3 days!

4. Cell Division
When a cell reaches the point at which the surface area is no longer able to sustain the volume, the cell divides!
By dividing, the cell produces 2 new, smaller cells with an adequate amount of cell membrane to maintain the cytoplasm

5. Types of Cells Somatic (AKA Body Cells) Make up all body structures
In each cell there are 46 chromosomes
There are 23 pairs of chromosomes
One of each pair comes from each parent
(i.e. 23 from mom and 23 from dad for a total of 46)
Germ (AKA Sex Cells)
Make up gametes (egg and sperm only)
Contain 23 chromosomes
WHY?

6. Cell Division
Both of these cells have to reproduce and divide but they do it in very different ways
Somatic Cell Division = mitosis
Germ Cell Division = meiosis

7. Somatic Cells Life cycle of a typical cell
Has 3 stages: Interphase, Mitosis and Cytokinesis

8. Cell Cycle

9. Cell Cycle Interphase Mitosis Cytokinesis Growth and prep DNA rep
Growth and Preparation
DNA Replication
More Growth and Preparation
Mitosis
Cytokinesis
Cell Cycle
Interphase
Growth and prep
DNA rep
Mitosis
Cytokinesis

10. Interphase Growth and prep: Reproduction: Cell increases in size
Makes proteins and molecules required for everyday
Some organelles begin to duplicate
Reproduction:
All 46 chromosomes makes a copy of themselves
Attached at centre by centromere, now has two sister chromatids
DNA is loose
RNA makes proteins in prep for replication

11. Copied Chromosome

12. Mitosis Division of the nucleus and its contents
Makes 2 daughter cells that are identical to the parent cell
Has 4 stages:
Prophase
Metaphase
Anaphase
Telophase

13. Pneumonic: Cell Cycle Order of events: Interphase Prophase Metaphase
Anaphase
Telophase
Cytokinesis
Pneumonic: In PE My
Aunt
Throws
Chairs!

14. Stages of Mitosis Prophase Chromosomes condense and become visible
Centrioles move to poles and make spindle fibres
Nuclear membrane disappears
Metaphase
Chromosomes line up along metaphase plate

15. Stages of Mitosis Anaphase
Spindle fibres pull chromosomes apart and towards the poles
Telophase
Nuclear envelope reforms around each set of chromosomes
Chromosome begin to decondense
Spindle fibres break down

16. Mitosis

17. Cytokinesis
The cells pinch apart forming two new daughter cells that are identical to the parent cell

19. Practice!!
Complete the worksheet!
Lab time! (pg 162)