Regulating the Cell Cycle
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Transcript of Regulating the Cell Cycle
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Regulating the Cell Cycle
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Cell Division Rates
• Cells do not all reproduce at the same rates
• Stomach cells, skin cells, blood cells and others reproduce often
• Nerve cells and most muscle cells do not reproduce at all once they are mature
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Cell Division Rates
• Many major medical issues that are being currently solved are related to cell reproduction– Cancer (Uncontrolled
Cell Reproduction)– Stem Cells (Cell
reproduction to damaged cells)
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Cell Cycle Regulators
• There are two different types of regulators that help a cell know when it is time to replicate– Internal regulators– External regulators
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Controls on Cell Division• Scientists can observe cell
division in Petri dishes containing different types of agar– This gives cells the food they
need to complete their cell cycles
• Cells on a Petri dish will grow until they form a thin layer– The cells will grow and divide
until they come in contact with other cells
– When this happens they will stop growing
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Controls on Cell Division
• If you take a full agar plate, and swipe away a section in the middle, what might happen?
• The cells will grow outward from the middle
• They will stop once they touch other cells
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Controls on Cell Division• This means that cells have
the ability to turn on and turn off their cell division
• When you get a cut, the cells grow inward to close the cut
• The process of being cut starts the process of being healed by activating these mechanisms
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Controls on Cell Division
• The same thing happens when bones break
• It is a more complex process than a cut, but it works on the same principals
• When bones break there is a separation between different types of cells that send signals to different tissues that action is needed
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Cell Cycle Regulators• Many different proteins
combine to help control cell division
• First major proteins found in the 1950’s were cyclins
• During cell reproductions, cyclin levels are higher
• During interphase, cyclin levels are lower
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Experiment
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Cell Cycle Regulators
• Proteins that respond to outside environmental factors are external regulators
• Growth factors are an example of external regulators– They are proteins or
steroids that stimulate cell growth and division
• Other molecules slow down cell growth
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Uncontrolled Cell Growth• Cancer is a disorder of
uncontrolled cell growth– Cancer cells don’t often
respond to signals that regulate the growth of most cells
– They form masses of cells called tumors
• Cancer cells can break loose and spread throughout the body
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Uncontrolled Cell Growth
• Various forms of cancer have been linked to smoking, radiation exposure and viral infections
• All cancer cells however have one thing in common– The uncontrolled
reproduction of cell division
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Uncontrolled Cell Growth• Many cancers can be caused
by a defective gene called p53– p53 normally halts the cell
cycle until all chromosomes have been replicated
• The p53 gene make a cell undergo apoptosis
• Apoptosis is a form of self destruction for the cell