Molecular diagnostics · USMLE Step 1

Which molecular diagnostic technique relies on fluorescently labeled probes that are cleaved by polymerase exonuclease activity during PCR to increase specificity?

  1. SYBR Green qPCR
  2. TaqMan qPCR assay
  3. Sanger sequencing
  4. Western blotting
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Correct answer: TaqMan qPCR assay

TaqMan qPCR uses a dual-labeled hydrolysis probe: during PCR, the Taq polymerase cleaves the probe if hybridized to target DNA, releasing fluorescence and providing highly specific quantitative detection.

Difficulty: Medium Question 11 of 21

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