1. Cell Division 2

2. Chromosomes

3. The Cell Cycle
1 CELL ENTERS…
2 CELLS LEAVE…

4. The Cell Cycle G1- “First Gap”- Cell grows
S- “DNA synthesis”- Chromosomes duplicate
G2- “Second Gap”- Cell prepares for cell division
M- “Mitosis”- Cell splits and cytokinesis occurs.

5. The Cell Cycle

6. Mitosis Mitosis can be thought of as the splitting of chromosomes.
4 main stages to memorize:
Prophase, Metaphase, Anaphase, Telophase
(PMAT)
Events of mitosis depend on mitotic spindle and the kinetochore region of each chromosome.

7. Stages of Mitosis
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE

8. Stages of Mitosis
Prophase- chromosomes condense and appear, nuclear envelope breaks down, mitotic spindle assemble with centrioles.
Metaphase- chromosomes line up at metaphase plate between 2 poles of the spindles.
Anaphase- Sister chromatids pulled apart by shortening of microtubules attached to centromeres. One set goes to each pole.
Telophase- Nuclear envelopes reform around each new set of DNA, chromosomes decondense and spread out.

10. Mitotic Spindle

11. Chromosome Migration During Anaphase

12. Overview What is important to understand is that:
Chromosomes are being pulled apart.
Sister chromatids (which have the same DNA) are being separated into separate daughter cells.

13. Cytokinesis The cytoplasm divides!
Cleavage furrow, a shallow groove in the cell surface near the old metaphase plate is evident.
Cell plate forms between 2 daughter plant cells.

14. Mitosis Movie Clips

15. Regulation of Cell Cycle
The timing and rate of cell division in different parts of a plant or animal cell are crucial to normal growth, development, and maintenance.
The frequency of cell division varies with the type of cell. Some cells constantly divide (skin cells) and some cells never divide (nerve cells).

16. Cell-Cycle Checkpoints

17. G2 Checkpoint
MPF (metaphase promoting factor) activity fluctuates with the level of cyclin in the cell.
Cdks (cyclin-dependent kinases) attach to cyclin to form MPF complex.
MPF triggers passage through the G2 checkpoint.

18. Cancer Cells
Cells respond to growth factors that stimulate cell division. When cells become too dense, density-dependent inhibition occurs because required growth factors and nutrients available to each cell are insufficient.
However, cancer cells have escaped these normal control mechanisms and therefore they divide and divide…

19. Tumor- mass of abnormal cell within normal tissue.
Benign vs. Malignant tumors
Metastasis- spread of cancer cells beyond original site.