Transcription Initiation: Promoters, General Factors and Polymerase Recruitment · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

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Science · Biochemistry & Molecular Biology · ages 19-21
Name ______________________   Date ____________

  1. Eukaryotic RNA polymerase finds a promoter alone and starts.

    Circle one:   True   False

  2. What is the first assembly step at a eukaryotic promoter?

    • TFIID gripping the TATA box
    • Polymerase arriving alone
    • TFIIH melting the duplex first

  3. What does TFIIH do in the preinitiation complex?

    • It degrades the polymerase tail
    • It recruits the next gene downstream
    • It melts the promoter and phosphorylates the polymerase tail

  4. How do activators and repressors act on initiation?

    • Activators recruit or stabilise the complex; repressors block assembly or escape
    • Activators melt DNA; repressors degrade RNA
    • Both bind the same site with the same effect

  5. Why is initiation, rather than elongation, the usual control point?

    • Elongation runs faster than assembly
    • Blocking a promoter shuts its gene cleanly, while stopping mid-gene wastes transcripts
    • Promoters are longer than whole genes

  6. How does bacterial initiation differ from the eukaryotic assembly?

    • Both use TFIID and TFIIH identically
    • Eukaryotes use sigma while bacteria use TFIID
    • Bacteria use one sigma factor; eukaryotes use many general factors

  7. A mutant TFIIH cannot phosphorylate the polymerase tail. What happens?

    • The enzyme idles at the start and no mRNA results
    • Elongation runs twice as fast instead
    • Sigma factor takes over the promoter

  8. Kim says stopping elongation is the cheapest way to silence a gene. What is wrong?

    • She is right; midway stops save the most energy
    • She wastes half-built transcripts and jams the template; blocking the start is cheaper
    • Elongation never happens, so the question is empty
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Answer key

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

Assemble first, then read W1-mt_0Ky-pYgh0Y-s1

  1. False · General factors must assemble and position it before anything starts.
  2. TFIID gripping the TATA box · TBP inside TFIID grips first, then helpers stabilise it.
  3. It melts the promoter and phosphorylates the polymerase tail · Melting plus tail phosphorylation licenses promoter escape.
  4. Activators recruit or stabilise the complex; repressors block assembly or escape · Regulators tune the firing rate by helping or hindering the complex.
  5. Blocking a promoter shuts its gene cleanly, while stopping mid-gene wastes transcripts · Control at the start is economical and precise.
  6. Bacteria use one sigma factor; eukaryotes use many general factors · One protein gives bacteria the specificity eukaryotes spread around.
  7. The enzyme idles at the start and no mRNA results · Without tail phosphorylation there is no licence to escape.
  8. She wastes half-built transcripts and jams the template; blocking the start is cheaper · Stopping mid-gene spends energy on RNA that is thrown away.
Worksheet · LightMySky