CRISPR: A Bacterial Defence Turned into a Tool · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

A filing system turned editor

Science · Microbiology · ages 20-22
Name ______________________   Date ____________

  1. For Cas9 sites with compatible PAMs, what directs sequence-specific targeting?

    • PAM recognition without guide pairing
    • Recognition of a target's total length by Cas9
    • Guide pairing with complementary target DNA

  2. What can become a spacer in a bacterial CRISPR array?

    • A short DNA fragment acquired from a phage or plasmid
    • A Cas protein retained after an earlier infection
    • An antibiotic bound between the array's repeats

  3. A stored spacer must supply RNA through transcription before its sequence can guide Cas9 defence.

    Circle one:   True   False

  4. End joining repairs a Cas9 break without copying a donor. Which description fits its possible outcomes?

    • Only a deletion, with no chance of accurate joining
    • An exact rejoin or a small insertion or deletion
    • Only an exact rejoin, with no sequence change

  5. What normally helps spare the stored spacer in a native Cas9 system?

    • Cas9 excludes targets on the host chromosome
    • The spacer lacks the required adjacent PAM
    • The spacer is removed when the guide is made

  6. A target base is A. A matching donor has G at that position. Which outcome could homology-directed repair using this donor produce, and how?

    • G replaces A through copying information from the matching donor
    • A remains because the donor only selects where Cas9 cuts
    • G replaces A because the guide itself acts as the repair donor

  7. Every new compatible DNA target requires a newly designed Cas9 protein, even when the guide can be changed.

    Circle one:   True   False

  8. A guide has a close DNA lookalike elsewhere beside a compatible PAM. What should researchers do about that site?

    • Exclude the site because its match is imperfect
    • Count the site as edited from its sequence match
    • Test the site for possible unintended cutting
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Answer key

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A filing system turned editor W1-mt_0joPWRvOLw-s1

  1. Guide pairing with complementary target DNA · The guide recognises complementary DNA by base pairing. Cas9 also requires a compatible PAM.
  2. A short DNA fragment acquired from a phage or plasmid · A spacer is a stored DNA sequence acquired from a source such as a phage or plasmid.
  3. True · Spacer DNA is the stored record. Transcription and RNA processing supply the RNA guide used with Cas proteins.
  4. An exact rejoin or a small insertion or deletion · End joining can restore the original sequence or leave insertions or deletions. Disruption is not inevitable.
  5. The spacer lacks the required adjacent PAM · Cas9 requires a compatible PAM as well as guide pairing. The native stored spacer lacks the required adjacent PAM.
  6. G replaces A through copying information from the matching donor · Copying the donor at that position can replace target A with G. Donor delivery alone does not guarantee this outcome.
  7. False · Changing the guide can redirect the same Cas9 protein to another site that meets its targeting requirements.
  8. Test the site for possible unintended cutting · Similarity and a compatible PAM identify a possible unintended target. They do not prove that cutting occurred.
Worksheet · LightMySky