What a Cell Has to Break to Become a Tumour · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The brakes a cell must lose to turn malignant

Science · Organisms & Life Processes · ages 22-23
Name ______________________   Date ____________

  1. A tumour grows without external growth signals. Which constraint was removed?

    • Dependence on neighbors for growth signals
    • The need for any DNA at all in the cell
    • The ability to attach to any surface it touches

  2. What do cell cycle checkpoints do in a healthy cell?

    • Block the cycle until each stage is done
    • Force division even when the DNA is badly damaged
    • Dissolve every bit of contact with neighboring cells

  3. A single mutation is usually enough to turn a healthy cell into a tumour.

    Circle one:   True   False

  4. Why does full transformation typically take years?

    • Cells divide far too fast to mutate in any possible way
    • Each layer must fall through mutation and selection
    • Checkpoints repair every single lesion within a few days

  5. A line keeps dividing after crowding, ignoring its neighbors. What broke?

    • The ribosome, so no proteins are ever made at all
    • The membrane, so nothing can ever enter it
    • Contact inhibition from crowding

  6. Cells with a stuck accelerator still do not transform. What best explains it?

    • The accelerator was never actually stuck on at all
    • Remaining brakes, death and limits still hold
    • Growth signals always prevent any cancer from forming

  7. A report listing three mutations with no explanation is already mechanistic. True or false?

    Circle one:   True   False

  8. Irradiated cells survive damage that should kill them. Which constraint does this test?

    • Growth factor dependence in the surrounding medium
    • The death and repair response
    • The speed of routine protein synthesis
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The brakes a cell must lose to turn malignant W1-mt_cjg3DtLHQL-s1

  1. Dependence on neighbors for growth signals · Self sufficiency in signals removes the cell's dependence on its neighbors.
  2. Block the cycle until each stage is done · Checkpoints enforce the rules by halting division until conditions are right.
  3. False · Overlapping safeguards compensate, so transformation needs several fallen layers.
  4. Each layer must fall through mutation and selection · Defeating each safeguard needs sequential rounds of mutation and selection.
  5. Contact inhibition from crowding · Resistance to stop signals removes the crowding brake on division.
  6. Remaining brakes, death and limits still hold · Redundancy means one removed brake still leaves others guarding the cell.
  7. False · Mapping lesions to removed constraints turns a catalogue into an explanation.
  8. The death and repair response · Irradiation probes repair and death, so survival points at that safeguard.
Worksheet · LightMySky