1. Click on picture for cell cycle animation – will go to www.cancerquest.org
)
2. Use alt-tab keys to go between website and power point presentation.
3. Click on blank space to proceed to next slide.)

There are several factors that regulate the cell cycle and assure a cell divides correctly.
1.Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If
DNA does not copy itself correctly, a gene mutation occurs.
DNA replication animation:click on DNA picture

2. Chemical Signals tell a cell when to start and stop dividing.
(Target cells animation: click on go sign)

Neighboring cells communicate with dividing cells to regulate their growth also.
(Normal contact inhibition animation: click on petri dish)

Cancer is a disease of the cell cycle . Some of the body’s cells divide uncontrollably and tumors form.
Tumor in Colon
Tumors in Liver

DNA mutations disrupt the cell cycle.
Mutations may be caused by:
1. radiation
2. smoking
3. Pollutants
4. chemicals
5. viruses

While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.
2 animations of cancer cells dividing: click on picture

Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors.
Skin cancer
(cancer cells dividing: click on picture.)

Normal Cell Division Cancer Cells
1. DNA is replicated properly.
2. Chemical signals start and stop the cell cycle.
3. Cells communicate with each other so they don’t become overcrowded.
1. Mutations occur in the
DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumors form.

Treating Cancers
Cancer treatments include drugs that can stop cancer cells from dividing.

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