The Neutral Theory and Reading a Molecular Clock · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading time in silent typos

Science · Genetics & Evolution · ages 19-20
Name ______________________   Date ____________

  1. Two lines differ at 60 spots and the rate is 2 per million years. What is the split age?

    Answer: ______________

  2. Why do neutral differences tick like a clock?

    • Chance fixes them at the typo rate
    • Selection speeds each one up
    • They never get fixed at all

  3. What job does a dated remain do in a clock study?

    • It decorates the lab wall
    • It anchors one split to real years
    • It slows all mutations down

  4. Why do short lived fast breeders tick faster per year?

    • More copying rounds per century
    • Larger body size
    • Slower metabolism

  5. How does a tightly guarded gene tick next to a free stretch?

    • They tick faster
    • They tick the same
    • They tick slower

  6. Why average over long stretches instead of one short gene?

    • Single genes are always exact
    • Chance makes short reads noisy
    • Long reads cost less

  7. A friend says one universal tick dates every gene. Is that right?

    • Yes, one tick fits all
    • Yes, anchors are optional
    • No, each gene and branch needs its own anchor

  8. Mice and elephants share one gene. Whose copy ticks faster per century?

    • The fast breeder line
    • The slow breeder line
    • Both tick identically
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Answer key

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

Reading time in silent typos W1-mt_yIidVpa703-s1

  1. 30 · Sixty gaps split by a rate of two per million years gives thirty million years.
  2. Chance fixes them at the typo rate · Neutral typos escape selection, so their fate is decided by chance alone.
  3. It anchors one split to real years · A dated remain converts relative genetic distance into absolute time.
  4. More copying rounds per century · More rounds per century means more copying slips per year.
  5. They tick slower · Guarded regions weed out most edits, so fewer neutral hits survive there.
  6. Chance makes short reads noisy · Averaging smooths the randomness and exposes the steady hidden rate.
  7. No, each gene and branch needs its own anchor · Constraint and generation pace differ, so serious work anchors each part alone.
  8. The fast breeder line · Copying rounds per unit time set the pace, so frequent copiers pile more slips.
Worksheet · LightMySky