Lesson eLearning

Which of the following statements about off‑target effects of CRISPR‑Cas9 compared with Zinc‑Finger Nucleases (ZFNs) is correct?

medium MCQ 1 mark Class 12 · Biology · Biotechnology and Its Applications
  1. Option A: CRISPR‑Cas9 generally shows higher off‑target activity than ZFNs because its guide RNA can tolerate mismatches.
  2. Option B: ZFNs have higher off‑target activity than CRISPR‑Cas9 due to their protein‑DNA binding domains.
  3. Option C: Both CRISPR‑Cas9 and ZFNs have negligible off‑target effects under all conditions.
  4. Option D: CRISPR‑Cas9 off‑target effects can be reduced by using paired nickases, whereas ZFNs cannot be modified for higher specificity.
Answer
Option A: CRISPR‑Cas9 generally shows higher off‑target activity than ZFNs because its guide RNA can tolerate mismatches.

Step-by-step solution

  1. Recall that off‑target effects refer to unintended cleavage at DNA sites that are similar but not identical to the intended target.
  2. Understand that CRISPR‑Cas9 uses a short RNA guide; mismatches between the guide and DNA can still be tolerated, leading to cleavage at near‑matches.
  3. Recognize that ZFNs rely on protein‑DNA interactions that are usually more stringent, giving them lower off‑target frequencies under comparable conditions.
  4. Compare the two systems and identify the statement that correctly describes this difference, which is option A.
Common mistake: Assuming ZFNs have no off‑target activity and are always more specific than CRISPR

Concept tested: Off‑target effects of genome‑editing tools

Published · How this solution was prepared and checked

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