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The Cell Cycle

The Cell Cycle. Regulation. Cells divide at different rates:. Some cells do not divide once they have developed. (muscles, nerves) Some cells divide very rapidly (skin, blood). Density Dependent Inhibition:. Cells will divide to fill up space.

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The Cell Cycle

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  1. The Cell Cycle Regulation

  2. Cells divide at different rates: • Some cells do not divide once they have developed. (muscles, nerves) • Some cells divide very rapidly (skin, blood)

  3. Density Dependent Inhibition: • Cells will divide to fill up space. • When the space is filled they will stop dividing. • Being crowded limits cell division.

  4. Cyclins: • Regulate the timing of the cell cycle. • Proteins • High levels of cyclin cause the cell to begin mitosis.

  5. Internal Regulators: • Proteins that respond to events inside the cell. • Example: proteins do not let the cell enter mitosis until all chromosomes have duplicated.

  6. External Regulators: • Proteins that respond to events outside the cell. • Sometimes called growth factors.

  7. Uncontrolled Growth • Cancer: disorder in which the cells do not respond to growth regulators. • Tumors of cells begin to grow. • All are caused by breakdown of the cell cycle.

  8. Causes of Cancer: • Many cancer cells have a defect in a gene called p53, which normally halts the cell cycle until all chromosomes have been duplicated. • Cancer cells often have abnormal numbers of chromosomes or defective chromosomes.

  9. Environmental Causes: • Tobacco usage • Some chemicals • Ultraviolet radiation • Viral infection of some types

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