The Cell Cycle and Cancer

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The Cell Cycle and Cancer

• AP Biology

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Cell Cycle

• Numerous genes control the cell cycle
• They regulate the progression through
  checkpoints. A sensor detects faulty or
  incomplete cell cycle events such as DNA damage.
  A signal is sent from the sensor to an effector
  that can stop the cell cycle until the problem
  has been resolved.

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Checkpoints
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What does the controlling?

• Kinases are enzymes that add phosphate groups to
  proteins (phosphorylation)
• There are over 500 of these kinases
• They take phosphates from ATP and transfer them
  to proteins, changing the shape (and function)

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What does the controlling?

• Often, kinases are present, but they must be
  activated by attaching to a cyclin, another
  protein. These kinases are called
  cyclin-dpendent kinases, or Cdks. A Cdk and
  its cyclin are referred to as a cyclin-Cdk
  complex.

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What does the controlling?

• They are the core of cell cycle control,
  triggering or turning off activities.
• The concentrations of Cdk and cyclin usually rise
  and fall together in the cell.
• This system keeps the cell from dividing when it
  should not divide

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What is cancer?

• Cancer is the inappropriate proliferation of
  cells
• If the cell checkpoints are not in place, this
  inappropriate proliferation can occur.
• Too much mitosis!
• Forms a mass or tumor

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What causes cancer?

• Mutations in the genes encoding the proteins that
  control the cell cycle. (genes that code for the
  kinases and cyclins)
• Oncogenes genes that have a normal function,
  but that when mutated, may cause cancer.

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Oncogenes
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What causes cancer?

• Oncogenes may be altered by mutagens such as UV
  light, chemicals, radiation, viruses, or a
  genetic predisposition
• Typically dominant, meaning only one of your two
  genes must be mutated to cause the altered cell
  functions

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What causes cancer?

• Tumor Suppressor genes can halt progression of
  the cell cycle.
• If these are mutated, cells divide when they
  should not
• BRCA I is a gene that produces a protein that
  works with other proteins to repair DNA damage.
  (a type of tumor suppressor)

Usually takes a hit in both types of genes ( and
their resulting proteins to cause cancer.
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Tumor Suppressor Genes