9-3 Cell Cycle RegulationPg. 253-257

•The average human cell has a cycle of about 20 hours.

•Not all cell types divide at the same rate

Normal Cell Cycle

•A combination of 2 substances signal the cellular reproduction.

1. Cyclins (Proteins)

2. CDKs (Cyclin-dependent kinases)-enzymes.

•Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.

•The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.

•Spindle checkpoints also have been identified in mitosis. If no spindle fibers are detected, the cycle is stopped.

Abnormal Cell Cycle: Cancer

Cancer- Uncontrolled growth & division of cells-a failure in the regulation of the cell cycle.

•Crowd out normal cells resulting in the loss of tissue function which can kill an organism.

•Spend less time in interphase than normal cells

•Cancer cells often have an abnormal, irregular shape compared to normal cells.

Contact Inhibition

Contact Inhibition- when cells touch one another, the rate of division slows or stops

• It’s a type of cell-to-cell communication by secreting chemical signals

• When changes occur in the genetic control of these chemicals, cancer can result

Demonstrating Contact Inhibition

Normal cells in dish

When cells are removed, cells at the edge of gap begin to divide

Normal cells stop dividing when bottom of dish is covered.

Cancer cells continue to divide, piling on top of each other

Causes of Cancer

Cancer is caused by mutations in segments of DNA that control the production of proteins regulating the cell cycle.

Carcinogens- substances and agents that are know to cause cancer.

Cancer Cells Video

Environmental Carinogens

•Cigarette smoke and tobacco of all kinds.

•Air & water pollution

•Exposure to ultraviolet radiation from sun

•Poor diet

Skin Cancer Video

Environmental Causes of Cancer

• Infection with certain virusesDNA Viruses

Epstein-Barr virus linked to Burkitt's lymphoma. Hepatitis B virus linked to liver cancerHuman papilloma viruses linked to cervical cancer. Human herpes virus-8 has been linked to the development of Kaposi sarcoma.

RNA VirusesHuman T lymphotrophic virus type 1 (HTLV-I) linked to T-cell leukemia.Hepatitis C virus linked to liver cancer.

BN Video Cancer Caused by Viruses

Apoptosis

Apoptosis- programmed cell death in our bodies…cells shrink and shrivel in a controlled process.

•Examples:- leaves falling in autumn

-Cells with DNA damage that could lead to cancer.

Stem Cells

Stem Cells- unspecialized cells that can develop into specialized cells under the right conditions.

• 2 Types of Stem Cells

Embryonic (ESC)

Adult (ASC)

Stem cell research video

http://learn360.com/ShowVideo.aspx?ID=142030

Embryonic Stem Cells

•Come from a fertilized egg consisting of 100-150 unspecialized cells

• If separated, these cells can develop into a variety of specialized cells.

• Controversial because it can destroy embryo if cells are taken

Adult Stem Cells

•Found in various types of tissue in the body. Used to maintain and repair the same kind of tissue

•Limited specialization

•Less controversial because the cells can be obtained with the consent of their donor

Stem Cell Research