LEQ: Why is the eukaryotic cell cycle regulated?

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LEQ Why is the eukaryotic cell cycle regulated?

• Key terms cyclin, growth factor, kinase
• Reading 5.3 (cancer)

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• Activator
• Briefly explain why the daughter cells resulting
  from mitosis are genetically identical to each
  other and to the original parent cell.

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Cells respond to internal and external signals
that regulate cell division.

• Cell communication
• physical contact with cells
• Cell signaling
• Receptors/enzymes
• soluble chemical signals
• Growth factors
• Survival signals

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Internal and external factors Example

• Cell adhesion (stops cycle)
• Positional information to nucleus
• integrins

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All cells rely on cell signaling to detect and
respond to cues in their environment

• Receptor Tyrosine Kinase (RTKs) activation
  involves binding to a signal (ligand), the
  joining together and phosphorylation of proteins.
• Growth promoting

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Signaling pathways

• Prevent division or,
• Promote cell division
• Ras pathways promote cell division by turning on
  genes/proteins associated with the cell cycle

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Cdks coordinate passage through checkpoints

• Checkpoints
• G1/S
• Restriction/ enter S
• G2/M
• Enter M
• Spindle/metaphase
• Exit M

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• Cyclins activate Cdks
• Timing of each phase can be adjusted
• Failure/DNA damage can result in cell death.
• apoptosis

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• Cell cycles can vary based on stages of
  development

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Programmed cell death purges damaged cells to
prevent disease and shape development

• Apoptosis is programmed cell death
• Initiation of death proteins (caspases)
• self-destructive enzymes
• Results in progressive cell destruction
• animation

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Pair Question

• Suppose a mutation in a Cdk gene causes the Cdk
  protein to change shape so it spontaneously
  activates without the aid of cyclins. Predict
  what would happen to the cell.
• Suppose a mutation in a caspase gene causes a
  Caspase protein to change shape so it
  spontaneously activates without the aid of a
  signaling molecule. Predict what would happen to
  the cell.

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• Competition in a tissue for growth factors
  sculpts a tissue
• Loss of tails
• Finger webbing

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• Leaf senescence (fall) is programmed cell death!

• Leaf development is programmed, seasonal cell
  growth!

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Telomere shortening leads to senescence and
programmed cell death
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