Multiple choice

The protein coded by a tumor suppressor gene in humans is

  1. a protein which controls progression through the cell cycle

  2. a protein which helps prevent apoptosis

  3. a protein which codes for a DNA repair enzyme

  4. a protein which forms fractions of a growth factor signalling pathway

  5. a protein which acts by opposing the action of PI3K
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A Correct answer
Explanation

Tumour suppressor genes code for proteins which normally control progression through a cell cycle checkpoint. These genes only contribute to a cancer when both copies are mutated in a way which produces an inactive protein product. A single mutation inactivating one gene only has no effect. They contribute to cancer because the absence of the protein product removes controls on cell division.

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