Stochastic Gene Expression: Bursting, Noise and Cell-to-Cell Variation · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Why identical cells disagree

Science · Genetics & Evolution · ages 22-23
Name ______________________   Date ____________

  1. In the two-colour experiment both copies glow brighter together in big cells. Which noise is this?

    • Intrinsic noise
    • Measurement magic
    • Extrinsic noise

  2. Two genetically identical cells hold different amounts of one protein. What process best explains this?

    • Transcriptional bursting
    • Different genomes in each cell
    • No RNA exists in cells

  3. Burst frequency means how often a gene switches on.

    Circle one:   True   False

  4. A mutation doubles protein made per on spell without touching switching. Which knob moved, and what happens to the mean?

    • Burst size moved; the mean rises
    • Burst frequency moved; the mean falls
    • Neither knob moved; nothing changes

  5. Red and green copies disagree sharply inside single cells, though the flask looks uniform. What dominates?

    • Extrinsic noise from the flask medium
    • Intrinsic noise from small molecule numbers
    • Identical timing in every cell

  6. A population keeps a few hardy cells that regrow the group after stress. How is its variation best described?

    • A nuisance that must be averaged away
    • A bet-hedging tool the cells exploit
    • Proof the cells have different genomes

  7. Averaging a population always removes the need to think about bursting, since the mean tells the whole story.

    Circle one:   True   False

  8. Mean protein doubles after a drug. Spread analysis shows variance patterns of more frequent switching, not bigger piles. What changed?

    • Burst size grew
    • The genome sequence changed
    • Burst frequency grew
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Answer key

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

Why identical cells disagree W1-mt_YD6DOmrvng-s1

  1. Extrinsic noise · A shared swing across both copies comes from a cell-wide cause like size.
  2. Transcriptional bursting · Bursty on-off firing makes identical cells differ by chance.
  3. True · Frequency counts on spells; size counts protein per spell.
  4. Burst size moved; the mean rises · Protein per spell is burst size, and more per spell lifts the mean.
  5. Intrinsic noise from small molecule numbers · Private colour gaps inside one cell mean each copy fires on its own.
  6. A bet-hedging tool the cells exploit · Survivors rebuilding the group show noise put to work.
  7. False · Averages hide fate choices and hedging that live in the spread.
  8. Burst frequency grew · Mean plus spread together separate the knobs, and here frequency moved.
Worksheet · LightMySky