Unlock hundreds more features
Save your Quiz to the Dashboard
View and Export Results
Use AI to Create Quizzes and Analyse Results

OR
Sign inSign in with Facebook
Sign inSign in with Google
Quizzes > Quizzes for Business > Healthcare

Test Your Skills: Laboratory COVID PCR Testing Knowledge Test

Assess Your Lab PCR Testing Proficiency Now

Difficulty: Moderate
Questions: 20
Learning OutcomesStudy Material

Step into an interactive COVID-19 Knowledge Quiz designed to sharpen your expertise in laboratory COVID PCR testing. Joanna Weib invites lab technicians and students to test their skills with this editable lab quiz, covering sample prep, amplification, and result interpretation. Completing this challenge will deepen your grasp of PCR protocols and boost diagnostic confidence. For a broader overview of viral testing, try the COVID-19 Knowledge Assessment Quiz. Explore more quizzes and customize any question to fit your training needs.

What does PCR stand for?
Polymerase Crossover Recombination
Peptide Chain Reaction
Protein Crystallography Reaction
Polymerase Chain Reaction
Polymerase Chain Reaction describes the enzymatic amplification of DNA through repeated thermal cycles. It is the foundational technique used in molecular diagnostics including COVID-19 testing.
During the initial denaturation step of PCR, what happens to the DNA double helix?
Nucleotides are incorporated
Enzyme is inactivated
The two strands separate (denature)
Strands form hairpins
Denaturation breaks the hydrogen bonds between base pairs, converting double-stranded DNA into single strands. This step is essential so primers can anneal in the next cycle.
In an RT-PCR test for COVID-19, which molecule is first reverse transcribed into complementary DNA?
Viral RNA
Host DNA
Viral lipid
Viral protein
RT-PCR begins by extracting viral RNA from patient samples. Reverse transcriptase then converts that RNA into complementary DNA (cDNA) for subsequent amplification.
Which enzyme is essential to extend DNA strands during PCR?
Taq polymerase
Restriction endonuclease
Reverse transcriptase
Ligase
Taq polymerase is thermostable and catalyzes the addition of nucleotides to extend new DNA strands during PCR. Its heat resistance makes it ideal for cycling temperatures.
In qPCR assays, what does the Ct (threshold cycle) value represent?
The concentration of enzyme used
The total number of target copies
The cycle number where fluorescence surpasses the threshold
The temperature of primer annealing
Ct value marks the PCR cycle when the fluorescence signal exceeds background levels. A lower Ct indicates a higher starting concentration of the target sequence.
What is the primary role of a no-template control (NTC) in PCR assays?
To enhance primer binding
To detect contamination in reagents
To measure sample RNA concentration
To calibrate thermal cycler temperature
An NTC contains all PCR components except template; any amplification indicates contamination. It ensures that positive signals are due to target amplification only.
Which component can cause PCR inhibition if present in clinical samples?
Hemoglobin
Ethanol at low concentration
dNTPs
Sodium chloride
Hemoglobin and other blood-derived substances inhibit polymerase activity and fluorescence detection. Effective sample purification is needed to remove such inhibitors.
Why is MgCl2 concentration important in PCR reactions?
It degrades template DNA
It acts as a cofactor for DNA polymerase and affects primer annealing
It stops amplification after a set number of cycles
It binds to fluorescent dyes to generate signal
Mg2+ stabilizes the interaction between polymerase and DNA and influences the melting behavior of DNA duplexes. Optimal MgCl2 is key for efficient and specific amplification.
Increasing the annealing temperature in a PCR protocol primarily affects which aspect?
Rate of nucleotide incorporation
Denaturation efficiency
Specificity of primer binding
Fluorescence signal intensity
A higher annealing temperature favors perfect primer-template matches, reducing nonspecific binding. Too high a temperature, however, can decrease overall amplification yield.
In qPCR amplification curves, what does the exponential phase signify?
Background noise before amplification
Plateau where enzyme activity stops
Annealing and extension overlap
Period of logarithmic increase in product quantity
During the exponential phase, PCR products double each cycle in an ideal reaction. This phase is used to determine quantification metrics like Ct values.
A late Ct value (e.g., 38) in a COVID-19 PCR test most likely indicates what?
Low target concentration near the detection limit
Complete PCR inhibition
Thermal cycler malfunction
High viral load in the sample
A high cycle threshold implies few target molecules were present, requiring more cycles to reach detection. Such results should be interpreted carefully for possible borderline positives.
What is the purpose of including an internal extraction control in RT-PCR assays?
To increase target gene amplification efficiency
To adjust fluorescence thresholds
To verify successful nucleic acid extraction and amplification
To neutralize PCR inhibitors
An internal control is co”extracted and co”amplified to confirm that extraction and amplification steps worked. It helps distinguish true negatives from technical failures.
Which pipetting error can lead to inconsistent Ct values across PCR replicates?
Using filtered tips for all reactions
Calibrating pipette regularly
Inverting the tube instead of vortexing
Inaccurate volume dispensed
Variations in dispensed volumes alter reagent and template concentrations, affecting amplification efficiency. Precision and accuracy are critical for reproducible results.
What is a critical safety practice when handling COVID-19 samples for PCR?
Storing reagents at room temperature indefinitely
Using open bench for all steps
Ignoring decontamination between runs
Working in a biosafety cabinet with appropriate PPE
Performing sample handling in a biosafety cabinet with gloves, gown, and face protection minimizes exposure to infectious aerosols. Regular decontamination also prevents cross-contamination.
Why is a positive control included in each PCR run?
To reduce cycle times automatically
To serve as a template for negative samples
To confirm that reagents and cycling conditions produce a known detectable signal
To calibrate pipette tips
A positive control contains a known target and should amplify under correct conditions, verifying reagent integrity and protocol performance. It helps identify false negatives.
What is the optimal GC content range for primer design to ensure specific annealing in PCR?
10 - 20%
40 - 60%
80 - 100%
60 - 80%
Primers with 40 - 60% GC content strike a balance between melting temperature stability and reduced secondary structure. This promotes specific and efficient binding.
A qPCR standard curve exhibits a slope of -3.9. What is the approximate amplification efficiency?
80%
100%
50%
120%
Efficiency = (10^(-1/slope) - 1) - 100; with slope -3.9, E ≈ (10^0.256 - 1) - 100 ≈ 80%. Deviations from -3.3 reflect less-than-ideal performance.
In a melt curve analysis using SYBR Green, a secondary peak at a lower melting temperature typically indicates what?
Specific target amplification
Primer-dimer formation
Non-functioning dye
High template concentration
Primer-dimers melt at lower temperatures than true amplicons, showing extra peaks in melt analyses. Identifying these artifacts is key for assay validation.
What is a key advantage of one-step RT-qPCR compared to two-step RT-PCR for viral detection?
Ability to store cDNA for later use
Higher specificity due to separate reactions
More flexibility in primer design
Reduced risk of contamination and faster setup
One-step RT-qPCR combines reverse transcription and amplification in one tube, reducing handling and contamination risk while speeding up processing. It is preferred in high-throughput diagnostics.
In a multiplex RT-qPCR, the internal control consistently amplifies at a Ct of 38 while the SARS-CoV-2 target amplifies at 25. What does this suggest?
Complete assay failure
Partial PCR inhibition affecting the control
High viral load has inhibited internal control enzyme
Incorrect primer design
A delayed internal control suggests inhibitors are present but the abundant viral target still amplifies efficiently. This pattern indicates partial inhibition affecting lower-abundance targets.
0
{"name":"What does PCR stand for?", "url":"https://www.quiz-maker.com/QPREVIEW","txt":"What does PCR stand for?, During the initial denaturation step of PCR, what happens to the DNA double helix?, In an RT-PCR test for COVID-19, which molecule is first reverse transcribed into complementary DNA?","img":"https://www.quiz-maker.com/3012/images/ogquiz.png"}

Learning Outcomes

  1. Analyze key steps in COVID PCR workflow and protocols
  2. Identify common sources of error in PCR testing processes
  3. Evaluate sample preparation and reagent selection techniques
  4. Demonstrate understanding of thermal cycling parameters
  5. Interpret PCR amplification curves and result data
  6. Apply safety guidelines for handling infectious materials

Cheat Sheet

  1. Master the COVID-19 PCR Testing Workflow - Discover how each step - from swabbing that sample to watching genetic material light up during amplification - works together to catch the virus in action. By grasping sample collection, RNA extraction, reverse transcription, and amplification, you'll become a PCR pro who nails accurate results every time. CDC: Real-Time RT-PCR Diagnostic Panel Instructions
  2. Spot Common PCR Pitfalls - Learn how contamination, pipetting mix-ups, and mis-tuned thermal cyclers can trip up your experiment and generate false alarms. Staying vigilant about these error sources helps you troubleshoot on the fly and keep your data squeaky clean. Common pitfalls in PCR diagnostics
  3. Perfect Your Sample Prep - Solid RNA extraction and purification are like giving your reaction VIP treatment: pure, intact genetic material that's ready for amplification. Nail these techniques to prevent degraded samples from derailing your results. RNA extraction methods for COVID-19 testing
  4. Choose the Right Reagents - Picking top-notch primers and probes turns your PCR assay from meh to marvelous in sensitivity and specificity. Understanding how these little DNA detectives work ensures you only amplify the target you want. Primer and probe design for SARS-CoV-2 detection
  5. Optimize Thermal Cycling Parameters - Fine-tune your denaturation, annealing, and extension steps like a DJ mixing tracks to get the perfect amplification groove. Getting the temperatures and times just right supercharges your results. Thermal cycling optimization in PCR
  6. Decode Amplification Curves - Dive into those wavy PCR plots and learn how cycle threshold (Ct) values reveal the amount of viral RNA lurking in your sample. Sharp analysis will help you distinguish between "no virus" and "viral superstar" signals. Understanding Ct values in PCR
  7. Follow Biosafety Best Practices - Suit up in PPE, work inside biosafety cabinets, and treat every sample like it's packing a punch. These safety rules aren't just red tape - they keep you and your lab buddies out of harm's way. CDC: Laboratory Biosafety Guidelines for Handling and Processing Specimens Associated with COVID-19
  8. Implement Quality Control Checks - Include positive and negative controls in each PCR run to make sure your assay isn't pulling a fast one. Regular QC steps build trust in your data and flag issues before they become big headaches. Quality control in PCR testing
  9. Unpack Reverse Transcription Principles - See how viral RNA gets converted into complementary DNA (cDNA) for amplification, a crucial step in RT-PCR. Understanding the enzyme mechanics helps you tweak conditions for top performance. Reverse transcription mechanisms
  10. Use Internal Controls Wisely - Internal controls reveal if something's blocking the reaction or if your reagents are underperforming. Incorporating these checks makes your PCR assay bulletproof and reliable. Internal controls in PCR assays
Make a Quiz (FREE) Copy & Edit This Quiz Create a Quiz with AI

Healthcare Quizzes

Powered by: Quiz Maker