Molecular diagnostics · USMLE Step 1

Which of the following is a limitation of conventional PCR that led to development of Real-Time PCR (qPCR)?

  1. It cannot amplify DNA templates at all
  2. It needs gel electrophoresis to detect products
  3. Its sensitivity is so high contamination is inevitable
  4. It is unable to use RNA-derived templates
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Correct answer: It needs gel electrophoresis to detect products

Conventional PCR requires post-PCR processing (gel electrophoresis) to visualize amplification products, which is time-consuming and increases contamination risk — a limitation addressed by real-time PCR with in-cycle fluorescence detection.

Difficulty: Medium Question 10 of 21

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