1. Regulating the Cell Cycle
cells have a “clock” with checkpoints along the way in the cell cycle
chemical signals tell cells when to start and stop dividing at these checkpoints

2. Regulating the Cell Cycle

3. Amoeba Sisters Video
Click here to watch!

4. Cell Cycle Checkpoints
G1 Checkpoint
checks growth of cell and conditions of environment
if everything is good, then the cell proceeds to S phase
if the cell environment does not require division, the cell may enter G0

5. Cell Cycle Checkpoints
G1 Checkpoint
G0 phase
extended G1 phase
cell is neither dividing nor preparing to divide
some types of cells (nerve and heart muscle cells) go into G0 and continue to perform their main functions for the rest of the organism's life

6. Regulating the Cell Cycle

7. Cell Cycle Checkpoints
G2 Checkpoint
checks replication of chromatin and conditions of environment
if everything is good, then the cell proceeds to the M phase

8. Regulating the Cell Cycle

9. Regulating the Cell Cycle
M Checkpoint
checks if chromosomes are properly aligned during metaphase
if everything is good, then the cell completes cell division

10. Regulating the Cell Cycle

11. Why is regulating the cell cycle necessary?
if problems with DNA are caught, the cell cycle is halted and the cell attempts to:
correct the issue
complete DNA replication
repair the damaged DNA
complete apoptosis

12. Apoptosis programmed cell death
if cells are stressed due to the environment or have a genetic mutation in the DNA, a sequence of self-destruction is initiated
“Cell Suicide”
one cell dying may save the rest of the organism

13. Regulating the Cell Cycle

14. Cell Cycle Genetic Signals
the cell cycle has built-in genetic signals to tell cells when to start and stop dividing
proto-onco genes – genes that encourage cell division
tumor suppressor genes – genes that inhibit cell division

15. Cancer
a disorder in which some cells lose the ability to control their own growth
these cells divide uncontrollably resulting in a tumor
tumor – an abnormal growth of tissue, not necessarily cancerous

16. Cancer
involves a loss of control over the cycle, malfunction of the “brakes”
the malfunction is caused by a mutation to proto-onco genes and tumor suppressor genes (usually multiple mutations)
Mutation – a change in a cell’s genes (DNA)
Oncogenes – mutated proto-onco genes that stimulate excessive division

17. Cancer

18. Cancer
Cancer and metastasis

19. Lymphatic System
a network of lymph vessels and lymph nodes that is a part of the body’s immune system
collects fluid, waste material, and other things (like viruses and bacteria) that are in the body tissues
lymph vessels are a lot like the veins that collect and carry blood through the body but instead of carrying blood, these vessels carry a clear watery fluid called lymph

20. Lymphatic System

21. Lymph Nodes and Cancer
when cancer cells break away from a tumor, they can travel to other areas of the body through either the bloodstream or the lymph system
cancer in lymph nodes MAY be a sign that the cancer has spread (or could spread) through the lymphatic system to other parts of the body

22. Metastasis spreading of cancer from one area of the body to another
typically spreads through blood or lymph

23. Cancer and Cell Functions
uncontrolled division can compromise the function of the tissue where the dividing cells are located and ultimately may cause death
quickly-dividing cells spend a large amount of time in M phase
cells perform most of their normal functions while in interphase (G1)

24. Other Resources Pg 126-127 in your textbook
National Institutes of Health
(see “Related Links” sections also…)
National Cancer Institute