1. Cell Division Honors Biology Unit 3

2. What is the cell cycle? During the cell cycle, a “parent” cell grows and divides to form 2 “daughter” cells. The cycle has three main stages –Interphase –Mitosis –Cytokinesis

3. W hy does a cell need to divide? 1. DNA Overload DNA overload is when the DNA has too many tasks to do (such as making proteins) and not enough DNA to get the job done efficiently. To prevent DNA overload cells stay small to limit a cells work load.

4. 2. Material Transfer Materials move into and out of cells Cells need to take in materials such as oxygen, water and glucose. Cells need to get rid of materials such as carbon dioxide, salts, other waste. Large cells lose efficiency in this process – surface area and volume do NOT increase at the same rate. W hy does a cell need to divide?

5. Growing to an adult A.The size of the organism’s cells _________________________ A.The number of cells the organism has? ___________________________ Stays the same size Increases as it gets bigger

6. The Cell Cycle Animation

7. M G1 S G2

8. Stage 1 Interphase During Interphase cells: –Grow to mature size Mitochondria and chloroplasts are duplicated –Replicate (copy) DNA Each cell needs instructions –Prepare for cell division Centrioles become visible Most of a cells life is spent in Interphase.

10. Chromosomes Are made of DNA Each chromosome consists of sister chromatids attached at a centromere

11. Stage 2: Mitosis The cells nucleus divides into two nuclei There are four phases –Prophase –Metaphase –Anaphase –Telophase P M A T

12. Animal Cell Mitosis- Video

13. Prophase 1st stage of Mitosis Chromatin condenses into chromosomes Centrioles separate and a spindle fiber begins to form. Nuclear membrane breaks down

14. Prophase

15. Metaphase 2nd Phase of Mitosis Chromosomes line up in the middle of the cell. Each chromosome is connected to a spindle fiber.

16. Metaphase

17. Anaphase 3rd Phase of Mitosis The sister chromatids separate at the centromere and move to opposite ends of the cell.

18. Anaphase

19. Telophase 4th Stage of Mitosis Chromosomes gather at opposite ends of the cells and lose their shapes (return to chromatin form) Two new nuclear membranes form, one for each cell.

20. Telophase

21. Stage 3: Cytokinesis The cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes

22. Cytokinesis Cytokinesis in the Animal Cell Animated

23. Cytokinesis