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The Cell Cycle

The Cell Cycle. Section 1.4 Homework: Pg. 45 #1-6. Different cells have varying life spans. Which types of cells have the shortest life span? Why might this be?. Cells don’t divide constantly. Cell division is a carefully controlled process .

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The Cell Cycle

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  1. The Cell Cycle Section 1.4 Homework: Pg. 45 #1-6

  2. Different cells have varying life spans • Which types of cells have the shortest life span? • Why might this be?

  3. Cells don’t divide constantly Cell division is a carefully controlled process. • It only takes up only a small portion of the life cycle of a cell • controlled by proteins There are some cells who do not undergo cellular division (i.e. nerve cells) after a certain period of time. As a result, these cells cannot be regenerated if damaged.

  4. The cell cycle • Cell division • Mitosis and cytokinesis • B. Interphase • Phase of cell cycle where cell is not actively dividing. • Consists of: • 2 periods of growth (G1 and G2 phase) • 1 period of DNA replication (S phase) G1 phase S phase M phase G2 phase

  5. Cell Cycle Checkpoints – points in the cell cycle when protein signals determine whether cell division should or should not occur This allows the body to control the number of cellsand the rate of division

  6. Cell Cycle Checkpoints There are 3 major checkpointsalong the cell cycle. Eachcheckpointproducesproteinsthateithercaninhibit the cell cycle or allowit to move forward

  7. Major errors Cellsthat are not able to pass the checkpoints tend to have someform of error. Errorsinclude: • Insufficient nutrients are present • DNA has failed to replicate • DNA is damaged These types of signals should tell a cell to not divide.

  8. Consequences of failing a checkpoint • halting of the cycle • repair, if possible • programmed cell death, if repair not possible (apoptosis)

  9. Types of cell death Necrosis aka “traumatic cell death” • cells “die” when they are damaged due to: • exposure to toxic chemicals or conditions • physical forces Apoptosis aka “cell suicide” controlled sequence of events: • “suicide” genes code for proteins that kill the cells in specific situations. • cell contents are packaged for use by other cells

  10. Cancer and the Cell Cycle In normal cells... • cells respond to signals to divide • rate of division = rate of cell death

  11. In cancer cells... • mutations in DNA make cells unresponsive to normal signals • cells divide without meeting checkpoint requirements • cells fail to undergo programmed cell death • Uncontrolled division produces visible masses of cells (tumours). These cells are replacing normal functionning cells.

  12. Not all tumours are cancerous: BenignTumour MalignantTumour

  13. Metastasis • Metastasis – The spread of cancerous cells from one area to another • via circulatory system • New tumours are established in other tissues

  14. Causes of cancer • Direct cause: • Mutations in DNA • Risk factors: • Genetic influence (some cancers)- some genes may predispose an individual to a certain form of cancer. • Environmental factors – certain components of the environment may be considered a mutagen and cause genetic mutations. Whatdoes « Mutations in DNA » refer to?

  15. Recall... • Mutagen – An environmental agent that can produce DNA mutations Carcinogen – An environmental agent that can produce cancerous DNA mutations

  16. Carcinogens • Tobacco smoke • Radiation • Tanning beds • X-rays • Viruses • Human Papilloma Virus (HPV) • Chemicals • BPA in plastic • Teflon

  17. Diagnosis • Blood tests • Imaging technologies • endoscopy • x-ray • ultrasound • CT scan • MRI

  18. Examining cancer cells Methods: • Blood sample • Biopsy (tissue sample) Whenusingbothmethods, scientists observe the cellsunder the microscope to determine if the cells have : An irregularshape An irregular size

  19. Treatment • Surgery • cancerous tissue is physically removed • Chemotherapy • the patient takes medications to kill cancerous cells • Radiation therapy • Carefully-aimed doses of radiation are used to target and kill cancerous cells Doctors can administer one form of treatment, or a combination of any

  20. Reducing your risk • Avoid known carcinogens • Eat healthy! Important: Nothing can 100% prevent cancer; you can only lower the risk

  21. Homework Read 1.4 • Pg. 45 #1-6 Define: cancer, mutagen, carcinogen, benign, malignant, metastasis

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