Practice Test GeeksPCR - Polymerase Chain Reaction Certification Practice Test
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Data Analysis & Troubleshooting 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.

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  1. In an RT-qPCR experiment, the no-RT (minus-RT) control amplifies. What is the most likely cause, and what is the fix?

    Answer: Genomic DNA contamination; DNase-treat the RNA or design intron-spanning primers

    Amplification without reverse transcription means a DNA template, usually genomic DNA, is present.

  2. A DNA sample has an A260/A280 ratio of 1.5. What does this most likely indicate?

    Answer: Protein or phenol contamination

    Pure DNA is about 1.8, and lower ratios suggest protein or phenol, which absorb near 280 nm.

  3. A nucleic acid sample has a low A260/A230 ratio (for example, 1.0). Which contaminant is most likely?

    Answer: Guanidine salts or other chaotropic carryover from extraction

    Guanidine salts, phenol, and carbohydrates absorb near 230 nm, which lowers the A260/A230 ratio (ideally about 2.0-2.2).

  4. How does digital PCR (dPCR) quantify target without a standard curve?

    Answer: By counting positive partitions and applying Poisson statistics

    dPCR splits the sample into many partitions and uses the fraction of positive partitions with Poisson correction to calculate absolute copies.

  5. What is the main purpose of the MIQE guidelines?

    Answer: To define the minimum information needed to report qPCR experiments reproducibly

    MIQE (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) standardizes reporting so experiments can be reproduced.

  6. At 100% efficiency, about how many cycles apart are the Ct values for two samples that differ 10-fold in starting template?

    Answer: 3.3 cycles

    Since 2^3.32 ≈ 10, a 10-fold difference shifts Ct by about 3.3 cycles.

  7. Amplification curves for all samples have unusually low plateau fluorescence, but Ct values and replicates look normal. Which cause is most likely?

    Answer: A reduced fluorescent probe or dye signal, such as a degraded or under-dosed probe

    Normal Ct values with low end-point fluorescence suggest a weak reporter signal, not failed amplification.

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