Practice Test GeeksPCR - Polymerase Chain Reaction Certification Practice Test
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Principles & Techniques Flashcards

7 cards from real PCR practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Principles & Techniques flashcards as text

  1. Which additive is commonly used to improve amplification of GC-rich templates?

    Answer: DMSO or betaine

    DMSO and betaine reduce secondary structure and even out melting differences in GC-rich DNA.

  2. What is the effect of excessive Mg2+ concentration in a PCR reaction?

    Answer: Lower fidelity and more nonspecific amplification

    High Mg2+ stabilizes mismatched primer binding and lowers fidelity, producing extra bands.

  3. How does the dUTP/UNG (uracil-N-glycosylase) system prevent carryover contamination?

    Answer: UNG removes uracil from previous dU-containing amplicons before cycling, making them non-amplifiable

    Previous products made with dUTP are cleaved by UNG, while native template DNA with thymine stays intact.

  4. A no-template control (NTC) shows a band of the expected size. What is the most likely cause?

    Answer: Contamination of reagents with template or amplicon

    An NTC has no template, so a specific product points to contamination.

  5. What is the main purpose of gradient PCR?

    Answer: To test a range of annealing temperatures in one run to find the optimum

    A gradient thermal block runs different annealing temperatures across columns at the same time.

  6. Which primer design feature is generally recommended?

    Answer: GC content of 40-60% with a G or C clamp at the 3' end

    Balanced GC content and a modest 3' GC clamp promote stable, specific binding without dimer formation.

  7. In multiplex PCR, what is a key design requirement?

    Answer: Primer pairs should have similar Tm values and produce distinguishable amplicon sizes or labels

    Matched Tm values allow a shared annealing temperature, and distinct sizes or dyes allow detection of each target.

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