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MODIFIED from a slide show by Kim Foglia

MODIFIED from a slide show by Kim Foglia http://www.explorebiology.com/documents/37Ch12MitosisRegulation2005a.pdf. INTERPHASE = G 1 , S, G 2. G 2 - Gap 2 Grow Produce molecules & organelles needed for cell division. MITOSIS. G 1 - Gap 1 Grow by producing proteins & organelles.

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MODIFIED from a slide show by Kim Foglia

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  1. MODIFIED from a slide show by Kim Foglia http://www.explorebiology.com/documents/37Ch12MitosisRegulation2005a.pdf

  2. INTERPHASE = G1, S, G2 G2- Gap 2Grow Produce molecules & organelles needed for cell division MITOSIS G1- Gap 1Grow by producing proteins & organelles G0- Cell leaves cycle and stops dividingMost body cells in this phase S- Synthesis DNA replication Some can return to cycle with signal (Ex; Liver cells respond to injury)Some never divide again (Ex: Mature nerve, muscle cells)

  3. Cyclin-dependent kinases (Cdk’s) are present all the time but inactive unless combined with cyclins KINASES- Enzymes that workby adding a phosphate group to other molecules Presence of MPF triggers passage past G1 & G 2 checkpoints

  4. Cyclin levels change throughout cell cycle Fluctuating levels of different Cyclin-Cdk complexesseem to control all stages of cell cycle

  5. CANCER CELLS • Don’t respond to control signals • Lose density-dependent inhibition • Lose anchorage dependence • Telomerase enzymes maintain/replace telomeres Transformation- process that changes a normal cell into a cancer cell

  6. Telomeres protect DNA from being degraded Telomeres become shorter with each replication; shorter in older cells Telomerase enzyme lengthens telomeres Cancer cells have increased telomerase activity 2009Nobel PrizePhysiology/Medicine Discovery of Telomeres Jack Szostak Carol Greider Elizabeth Blackburn.

  7. Most cells divide 20-50 times in culture; then stop, age, die Cancer cells are “immortal” -HeLa cells from a tumor removed from a woman (Henrietta Lacks) in 1951 are still reproducing in culture http://www.sanger.ac.uk/Info/Press/gfx/081223_cells_300.jpg

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