1. The Cell Cycle

2. Eukaryotic Chromosomes

3. LE 12-4 0.5 µm Chromosome duplication (including DNA synthesis)
Centromere
Sister
chromatids
Separation
of sister
chromatids
Centromeres
Sister chromatids

4. INTERPHASE S (DNA synthesis)
LE 12-5
INTERPHASE S
(DNA synthesis) G1
Cytokinesis
Mitosis G2
MITOTIC
(M) PHASE

5. G1 Phase: Cell Growth
In the G1 phase, cells increase in size and synthesize new proteins and organelles.

6. S Phase: DNA Replication
In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

7. G2 Phase: Preparing for Cell Division
In the G2 phase, many of the organelles and molecules required for cell division are produced.

8. M Phase: Cell Division
In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.
Mitosis is the division of the cell nucleus.
Cytokinesis is the division of the cytoplasm.

9. Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.

10. Prophase
The centrioles move to opposite sides of nucleus and help organize the spindle.

11. Prophase
The spindle forms and DNA strands attach at a point called their centromere.

12. Prophase
The nucleolus disappears and nuclear envelope breaks down.

13. Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.

14. Metaphase
The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

15. Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.

16. Anaphase
The chromosomes separate into two groups near the poles of the spindle.

17. Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.

18. Telophase
A nuclear envelope re-forms around each cluster of chromosomes.

19. Telophase
The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.

20. Cytokinesis Cytokinesis is the division of the cytoplasm.
The process of cytokinesis is different in animal and plant cells.

21. Cytokinesis in Animal Cells
The cell membrane is drawn in until the cytoplasm is pinched into two equal parts.
Each part contains its own nucleus and organelles.

22. LE 12-9a
100 µm
Cleavage furrow
Contractile ring of
microfilaments
Daughter cells
Cleavage of an animal cell (SEM)

23. Cytokinesis in Animal Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
Instead, a cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.

24. LE 12-9b
Vesicles
forming
cell plate
Wall of
parent cell
1 µm
Cell plate
New cell wall
Daughter cells
Cell plate formation in a plant cell (TEM)

25. 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.

26. LE 12-6ca
INTERPHASE
PROPHASE
PROMETAPHASE

27. LE 12-6da
10 µm
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS

28. 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

29. 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

30. Lymph
vessel
Tumor
Blood
vessel
Glandular
tissue
Metastatic
tumor
Cancer cell
A tumor grows from a
single cancer cell.
Cancer cells invade
neighboring tissue.
Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
A small percentage
of cancer cells may
survive and establish
a new tumor in another
part of the body.