1. Section 8.2 Summary – pages 201 - 210
According to the cell theory, where do all cells come from?
Cells divide to make a new identical cell.
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2. Section 8.2 Summary – pages 201 - 210
At this moment, cells in your body are growing, dividing, and dying.
Old cells on your scalp, palms of your hands, and soles of your feet are shedding and being replaced.
Cuts and bruises are healing
Your intestines are producing millions of new cells each second.
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3. Section 8.2 Summary – pages 201 - 210
Early biologists noticed that just before cells divide, several short structures suddenly appeared in the nucleus.
Then they noticed that after cellular division that these structures would vanish.
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4. Section 8.2 Summary – pages 201 - 210
WAIT TO ANSWER: Where is DNA found in a eukaryotic cell?
Nucleus
For most of a cell’s life, DNA exists in long strands called chromatin.
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5. Section 8.2 Summary – pages 201 - 210
CELL REPRODUCTION
Before a cell divides, chromatin coils up into tightly packed structures called chromosomes.
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6. Chromosome

7. Section 8.2 Summary – pages 201 - 210
CELL REPRODUCTION
Chromosomes are the carriers of genetic material that is copied and passed from generation to generation of cells.
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8. Section 8.2 Summary – pages 201 - 210
CELL REPRODUCTION
Before a cell can divide- a copy of all the chromosomes needs to be made so that the new “daughter” cell has the exact DNA as the “parent” cell.
“Parent Cell” Chromosomes
“Daughter Cell” Chromosomes
Section 8.2 Summary – pages

9. TALK TO YOUR NEIGHBOR: (I will randomly call on someone in a few seconds)
DNA can be very stringy and called _______
When a cell is about to divide, it coils up tightly and is now a “fatter” structure called _________
Chapter Assessment

10. TALK TO YOUR NEIGHBOR: (I will randomly call on someone in a few seconds)
Why does a cell make a copy of it’s chromosomes before it divides and makes another cell?
Chapter Assessment

11. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
The cell cycle is the sequence of growth and division of a cell. (life cycle)
The cell cycle consists of Interphase, Mitosis, and Cytokinesis
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12. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
The majority of a cell’s life is spent in the growth period known as interphase.
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13. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
Interphase
During Interphase, under a microscope, there doesn’t appear to be much going on.
BUT, Interphase is the busiest phase of the cell cycle
During this time the cell is growing, making more organelles, and chromatin (DNA) is replicating.
Replicated Chromatin
Chromatin
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14. The Cell Cycle
Mitosis
Following interphase, a cell enters its period of nuclear division called mitosis.
There are four phases in mitosis…

15. Section 8.2 Summary – pages 201 - 210
PROPHASE:
The membrane around the nucleus and nucleolus disintegrate (disappear)
2. (In animal cells) centrioles begin to move to opposite ends of the cell and spindle fibers begin to form
Nucleus
Centrioles
Spindle Fiber
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16. Section 8.2 Summary – pages 201 - 210
3. Chromatin coils up to form visible chromosomes
Replicated Chromatin
Replicated Chromosome
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17. Section 8.2 Summary – pages 201 - 210
The two halves of the doubled structure are called sister chromatids.
Sister chromatids are identical to each other.
Sister chromatids
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18. Section 8.2 Summary – pages 201 - 210
Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis.
Centromere
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19. Section 8.2 Summary – pages 201 - 210
PROPHASE
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20. Section 8.2 Summary – pages 201 - 210
METAPHASE:
The chromosomes move to the middle (equator) of the cell
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21. Section 8.2 Summary – pages 201 - 210
Spindle fibers on attach to the centromeres on either side of the chromosome
Centromere
Spindle fibers
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22. Section 8.2 Summary – pages 201 - 210
METAPHASE
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23. Section 8.2 Summary – pages 201 - 210
ANAPHASE:
The spindle fibers pull on the centromeres, break them, and pull the sister chromatids apart to either side of the cell- toward the centrioles.
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24. Section 8.2 Summary – pages 201 - 210
ANAPHASE
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25. Section 8.2 Summary – pages 201 - 210
TELOPHASE:
1. Two complete cells are forming.
2. Chromosomes unravel back into chromatin
3. Nuclear membrane begins to re-appear around the chromatin
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26. Section 8.2 Summary – pages 201 - 210
TELOPHASE
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27. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
Cytokinesis
Following telophase, the cell’s cytoplasm completely divides in a process called cytokinesis.
This is the final step in the cell cycle.
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28. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
Cytokinesis
Cytokinesis differs between plants and animals.
Toward the end of telophase in ANIMAL cells, the plasma membrane pinches in along the equator.
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29. Section 8.2 Summary – pages 201 - 210
The Cell Cycle
Cytokinesis
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30. Section 8.2 Summary – pages 201 - 210
Cytokinesis
Plant cells have a rigid cell wall, so the plasma membrane does not pinch in.
A structure known as the cell plate is laid down across the cell’s equator.
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31. Section 8.2 Summary – pages 201 - 210
Result of Mitosis
When mitosis is complete, unicellular organisms remain as single cells.
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32. Section 8.2 Summary – pages 201 - 210
Result of Mitosis
Following mitosis, in multi-cellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function.
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33. Section 8.3 Summary – pages 211 - 213
Control of Cell Cycle
Occasionally , cells lose control of the cell cycle.
Cancer is a growth resulting from uncontrolled cell division.
This loss of control may be caused by environmental factors or certain inheritances.
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34. Section 8.3 Summary – pages 211 - 213
Control of Cell Cycle
There are enzymes (proteins) that control the rate of the cell’s life cycle.
Scientists believe that if something goes wrong with these enzymes, they cause cells to skip a long interphase and divide a lot faster than they should.
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35. Section 8.3 Summary – pages 211 - 213
CANCER
A bunch of cancer cells together form masses of tissue called tumors that deprive normal cells of nutrients.
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36. Section 8.3 Summary – pages 211 - 213
CANCER
The causes of cancer are difficult to pinpoint because both genetic and environmental factors are involved.
Cancer may also be caused by viral infections that damage the genes.
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