1. Chapter 12: The Cell Cycle
AP Biology
Chapter 12:
The Cell Cycle

2. One cell becoming two

3. Chromatin vs. Chromosomes appearance within the cell.

4. Fig: 19.4 Coiling up of Chromatin

5. Somatic cells vs. Germ cells The egg surrounded by sperm.

6. Fig: 12.4 Before and after the S phase

7. Mitosis (1 Division) vs. Meiosis (2 Divisions)

8. Interphase

9. Interphase cell (Look at the chromatin in the blue nucleus and the yellow cytoskeleton.)

10. Fig: 12.6 a

11. Cell in Prophase

12. Fig: 12.6 b

13. Cell in Metaphase

14. Cell in Anaphase

15. Cell in Telophase and starting Cytokinesis

16. Chromosome movement Kinetochore Tubulin subunits Motor Microtubule
LE 12-8b
Chromosome
movement
Kinetochore
Tubulin
subunits
Motor
protein
Microtubule
Chromosome

17. Animal vs. Plant

18. LE 12-10 Chromatin condensing Nucleus Chromosomes Cell plate 10 µm
Nucleolus
Prophase. The
chromatin is condensing.
The nucleolus is beginning to disappear.
Although not yet visible in the micrograph, the mitotic spindle is starting to form.
Prometaphase. We
now see discrete chromosomes; each
consists of two identical sister chromatids. Later
in prometaphase, the
nuclear envelope will fragment.
Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at
the metaphase plate.
Anaphase. The
chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro-
tubules shorten.
Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

19. Microscopic view of Mitosis in Onion root tips
Microscopic view of Mitosis in Onion root tips. Can you identify the stages?

20. LE 12-11_3 Cell wall Origin of replication Plasma membrane
E. coli cell
Bacterial
chromosome
Chromosome replication begins.
Soon thereafter,
one copy of the origin moves rapidly toward the other end of the cell.
Two copies
of origin
Origin
Origin
Replication continues. One copy of the origin is now at each end of the cell.
Replication finishes.
The plasma membrane grows inward, and
new cell wall is deposited.
Two daughter
cells result.

21. Checkpoints (Is all going according to plan?)

22. LE 12-15 G0
G1 checkpoint G1 G1
If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.

23. Relative concentration
LE 12-16a M G1 S G2 M G1 S G2 M
MPF activity
Cyclin
Relative concentration
Time
Fluctuation of MPF activity and cyclin concentration
during the cell cycle

24. Molecular mechanisms that help regulate the cell cycle
LE 12-16b G1
Cyclin S
Cdk
Degraded
cyclin M G2
accumulation G2
checkpoint
Cdk
Cyclin is
degraded
Cyclin
MPF
Molecular mechanisms that help regulate the cell cycle

25. Chromosome movement Kinetochore Tubulin subunits Motor Microtubule
LE 12-8b
Chromosome
movement
Kinetochore
Tubulin
subunits
Motor
protein
Microtubule
Chromosome

26. Cells anchor to dish surface and divide (anchorage dependence).
LE 12-18a
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete
single layer, they stop dividing
(density-dependent inhibition).
If some cells are scraped away, the
remaining cells divide to fill the gap and
then stop (density-dependent inhibition).
25 µm
Normal mammalian cells

27. Cancer cells do not exhibit anchorage dependence
LE 12-18b
Cancer cells do not exhibit
anchorage dependence
or density-dependent inhibition.
25 µm
Cancer cells

28. Malignant cancer cells from the breast (See the ABNORMAL “crab” shape of the cells.)