CHAPTER 10: Cell Division

1. CHAPTER 10: Cell Division

2. Why Cell Division? • (We will use the following analogy to understand cell division.) ANALOGY • A cell is like a town. • The DNA in the nucleus is like the books in a library. • The nucleus doesn’t grow and the DNA doesn’t increase in a cell.

3. Town Library Analogy • SITUTION: You have a research project. Your town has grown from 1000 to 10, 000 people, but the library is unchanged. • QUESTION: What is going to happen when you go to check out books for your project?

4. Town Library Analogy • ANSWER: Books won’t be available. The staff may be having a hard time restocking books, even if they have been returned.

5. Town Library Analogy • SOLUTION: Build another library in another section of town, stock it with additional copies of books.

6. CELL • The cell has the same 2 problems. • DNA Overload: The DNA gets to a point where it can’t do more things at the same time. • Exchange of Materials: After a certain size, the cell can’t efficiently transport nutrients (in) and wastes (out)

7. CELL • SOLUTION: The cell will make an exact copy of itself and divide. • 2 small cells with identical information and able to transport materials easily.

8. DNA Replication • DNA stores genetic information • It gets replicated (copied) before the cell divides • Therefore, each generation of cells is identical

9. CELL CYCLE: The process a cell repeats every time it divides

10. INTERPHASE: When the Cell is NOT Dividing • G1: & G2 phases: growth • S Phase: “synthesis”-when the DNA is replicated

11. 2 Important Parts of Cell Division 1. Mitosis-division of the nucleus 2. Cytokinesis-Division of the cytoplasm (cell splits)

12. MITOSIS ↓ CYTOKINESIS ↓

13. duplicated chromosome prophase chromatin • STAGE 1 OF MITOSIS: PROPHASE • DNA is Packaged into Chromosomes • Centrioles move to opposite sides of cell as spindle begins to form • Nuclear envelope breaks down

14. metaphase • STAGE 2 OF MITOSIS: METAPHASE • Chromosomes line up in center of cell • Each chromatid is attached to a spindle fiber at its centromere

15. STAGE 3 OF MITOSIS: ANAPHASE • Sister chromatids separate & • move to opposite ends of cell.

16. STAGE 4 OF MITOSIS: TELOPHASE • Chromosomes are at opposite ends of cell & become chromatin again • New nuclear envelopes form

17. Mitosis in Action Blue shows DNA, green shows spindle fibers.

18. AFTER MITOSIS: CYTOKINESIScell divides into 2 cells ANIMAL CELL: Pinches into 2 cells PLANT CELL: cell walls forms between 2 new cells

19. REGULATION OF CELL CYCLECyclins are chemicals that control cell division 1. Internal Regulators-cyclins inside the cell that control its division 2. External regulators- cyclins outside the cell that control its division

20. Example of Regulators • Internal: When you get a cut, your cells send out cyclins so that new cells will be made (cell division) • External: When the cells touch (cut is healed), cyclins tell cells to stop dividing.

21. Licentious division - prostate cancer cells during division. Cancer Is One Outcome of A Runaway Cell Cycle

22. CANCER: Regulators out of Control • Cancer: cells dividing out of control • Often an error in the p 53 gene that regulates cell division

23. Why Cancer is a Problem • Cancer cells aren’t poisonous • They rob your body of nutrients. • They can develop their own network of blood vessels. • Rob your body faster • Pathway for cancer to spread through your body. (“metastasis”)

24. Cancer Treatment Chemotherapy & Radiation are used to kill cancer cells. • Benefits: cancer cells are killed • Drawbacks: many healthy cells can be killed too.

25. Chemotherapy • Use of medications

26. Radiation • Use of exposure to radioactive elements, which destroy cells.