Microtubules, Dynamic Instability and the Spindle · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Microtubule switching and chromosome capture

Science · Organisms & Life Processes · ages 20-22
Name ______________________   Date ____________

  1. Which change favors catastrophe at a growing microtubule end?

    • Loss of the stabilizing GTP-rich cap
    • Continued addition maintaining a GTP-rich cap
    • Restoration of a stabilizing cap during rescue

  2. What is microtubule dynamic instability?

    • Steady growth without ever switching into shortening
    • Switching between growth and rapid shortening
    • Repeated splitting into two separate microtubules

  3. Which site forms the usual end-on attachment between a spindle microtubule and a chromatid?

    • Telomere at a chromosome end
    • Nucleosome along a chromosome arm
    • Kinetochore at the centromere

  4. A drug strongly suppresses spindle microtubule growth and shortening. Which prediction is supported?

    • Searching and attachment correction can suffer
    • Every existing attachment must disappear immediately
    • Chromosome separation must become more accurate

  5. How do repeated growth and shortening help spindle microtubules establish attachments?

    • They aim each end at a chromosome's known location
    • They sample space and contacts can be captured
    • They bring every chromosome to an unmoving end

  6. Rescue is a switch from microtubule shortening back to growth.

    Circle one:   True   False

  7. Once chromosomes have attached, microtubule dynamics are no longer needed for accurate division.

    Circle one:   True   False

  8. A student says kinetochore capture permanently stops all subunit turnover in that microtubule. Which correction fits?

    • Capture requires every tubulin subunit to stop changing
    • An attachment can persist while subunits turn over
    • Any subunit loss must first break the whole attachment
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Answer key

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

Microtubule switching and chromosome capture W1-mt_RWhMJxOmUu-s1

  1. Loss of the stabilizing GTP-rich cap · The GTP-rich cap stabilizes the growing tip. Losing it favors rapid shortening.
  2. Switching between growth and rapid shortening · A microtubule can switch from growth to rapid shortening and later return to growth.
  3. Kinetochore at the centromere · The kinetochore is the protein complex assembled at the centromere that provides this attachment.
  4. Searching and attachment correction can suffer · Reduced dynamics can impair searching and correction. This does not require all existing attachments to disappear.
  5. They sample space and contacts can be captured · Extension and withdrawal let searching ends sample space. Suitable contacts can become attachments.
  6. True · Rescue ends a shortening phase and allows growth to resume.
  7. False · Dynamics also support attachment correction and chromosome movement after initial attachment.
  8. An attachment can persist while subunits turn over · A maintained attachment does not require a microtubule to become permanently static.
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