1. The Cell Cycle & Mitosis

2. 2 Reasons why cells divide
1) Growth
2) Replace worn out or damaged cells

3. Cell Division in Eukaryotes
Called Mitosis
Cell Grows & copies its DNA before it can divide

4. The series of events that cells go through as they grow & divide ~ The Cell Cycle

5. 2 Phases of the Cell Cycle
Interphase
“M” Phase
Includes Mitosis & Cytokinesis

6. The Cell Cycle: G1 S G2 Prophase Metaphase Anaphase Telophase
Interphase
Mitosis

7. M G2 G1 S

8. Interphase: a growth period
G1 (Growth/Gap 1) –
Cell grows in size,
makes new organelles
performs assigned function
DNA is relaxed in chromatin and is not visible

9. Interphase: a growth period
S phase (Synthesis) –
duplicates DNA to prepare for mitosis
G2 (Growth/Gap 2) –
cell prepares for mitosis

10. Talk to a partner: Explain the phases of Interphase

12. Chromosomes condense and become visible at the start of mitosis

13. Chromatin DNA is relaxed; DNA appears as chromatin during interphase
Chromosome visible DNA during mitosis

14. Mitosis occurs in 4 phases
Prophase
Metaphase
Anaphase
Telophase

15. Vocab Terms
Sister chromatidsidentical halves of the duplicated parent chromosome
Centromerecell structure that joins the two sister chromatids of a chromosome

16. Prophase DNA organizes Nuclear membrane & nucleolus disappear.
Chromosomes are paired with their identical copies (sister chromatids held together by the centromere)
chromatin condense into visible chromosomes.
Nuclear membrane & nucleolus disappear.
Spindle fibers form between the centrioles, located at opposite ends of the cell
Prophase

18. Metaphase Chromosomes line up in the middle of the cell.
Each chromatid is attached to a separate spindle fiber by its centromere.

20. Anaphase
Sister chromatids are pulled apart to opposite poles of the cell.

22. Telophase 2 identical daughter cells are formed.
Cytokinesis occurs (the division of the cytoplasm) as the plasma membrane pinches in along the equator.
Nucleolus and nuclear membrane reappear, chromosomes begin to uncoil & relax back into chromatin

24. In plants…
Because plant cells have a cell wall, the plasma membrane does not pinch in.
Rather a structure known as the cell plate forms across the cell’s equator.

25. Plant in cytokinesis
It’s hard to see, but there is a cell plate forming in the middle of the cell, next to the arrow.

26. Finally…
After mitosis is complete, each new daughter cell is an identical copy of the parent cell. Both cells enter interphase to carry out their assigned function until they are ready to divide.

27. All together now…

28. Talk to a partner: Explain the phases of Mitosis

29. Cell Cycle practice

30. What happens when the cell is not growing or dividing?
Cell is resting

31. Cell enters G0 phase, where cell is resting and carrying out its normal function

32. When cells are damaged and need repair or need to be replaced, cell will reenter the cell cycle

33. Controlling Cell Growth Through Gene Regulation
Cell division stops when cells touch
Can resume if space is available (injury)

34. Talk to a Partner: Do Cells Grow Indefinitely?
Section 10-3
If center cells are removed, cells near the space will start to grow again.
SHOWS: Cell division
genes can be turned on
and off
Cells grow until they touch other cells

35. What happens when the genes that control cell division become damaged?
Some cells do not respond to the signals that regulate the growth
Result ~ uncontrolled cell growth: cancer
Causes of cancer:
cigarette & tobacco use
radiation exposure (X-ray & UV light)
genetics
some viruses

37. Cancer Video

38. Stem Cells Stem cells - unspecialized cells
Through cell differentiation – stem cells become specialized in structure and function
Two Types: Embryonic and Adult Stem Cells

40. Cornell Summary