LATEST AMT MOLECULAR DIAGNOSTICS TECHNOLOGIST (MDT)
CERTIFICATION EXAM ACTUAL 2026/2027 COMPLETE APPROVED
QUESTIONS AND CORRECT DETAILED ANSWERS WITH
RATIONALES (100% CORRECT VERIFIED SOLUTIONS) NEWEST
UPDATED VERSION 2026 EDITION |GUARANTEED PASS A+ (BRAND
NEW!) |INSTANT PDF DOWNLOAD
1. A clinical laboratory is validating a new real-time PCR assay for Chlamydia
trachomatis. The technician runs a panel containing 20 known positives and 20
known negatives. Three positive samples yield no amplification, and two negative
samples show late amplification (Ct > 38). What is the diagnostic specificity of this
assay based on these results?
A) 85%
B) 90%
C) 95%
D) 100%
Correct Answer: B) 90%
Rationale: Specificity = True Negatives / (True Negatives + False Positives) ×
100. Here, true negatives = 20 total negatives minus 2 false positives = 18. So 18 /
20 = 0.90 or 90%. The false positives (late amplification) reduce specificity.
2. A molecular technologist observes that after each amplification cycle in a real-
time PCR run, the fluorescence signal increases but the Ct value for the positive
control is delayed by 4 cycles compared to the expected value. The most likely
cause is:
A) Incorrect annealing temperature
B) RNA contamination in the master mix
C) Reduced efficiency of the DNA polymerase
D) Excess template concentration
Correct Answer: C) Reduced efficiency of the DNA polymerase
Rationale: Delayed Ct indicates slower amplification kinetics. Reduced
polymerase efficiency (e.g., due to old enzyme, inhibitors, or suboptimal buffer)
directly increases Ct. Incorrect annealing usually causes no amplification or
nonspecific products. RNA contamination does not affect Ct of DNA targets.
Excess template would decrease Ct.
,3. Which of the following next-generation sequencing (NGS) library preparation
steps is responsible for attaching sample-specific barcodes to each DNA fragment?
A) Fragmentation
B) End repair
C) Adapter ligation
D) Size selection
Correct Answer: C) Adapter ligation
Rationale: During adapter ligation, sequencing adapters that include unique
barcode/index sequences are attached to both ends of fragmented DNA.
Fragmentation shears DNA, end repair creates blunt ends, and size selection
purifies fragments by length.
4. A patient specimen is received for HIV-1 viral load testing using reverse
transcription PCR (RT-PCR). The technologist forgets to add the reverse
transcriptase enzyme to the master mix. What will be the result?
A) No amplification because cDNA cannot be synthesized
B) Amplification will be normal because DNA polymerase substitutes for RT
C) Late amplification due to partial RNA degradation
D) Fluorescence signal only in the no-template control
Correct Answer: A) No amplification because cDNA cannot be synthesized
Rationale: RT-PCR requires reverse transcriptase to convert viral RNA to
complementary DNA (cDNA). Without RT, no cDNA is produced, and subsequent
PCR cannot amplify the RNA genome. DNA polymerase cannot use RNA as a
template.
5. In a melt curve analysis following SYBR Green real-time PCR, a single sharp
peak is observed at 82°C for all samples, but the no-template control shows a
smaller peak at 78°C. This indicates:
A) Specific target amplification with primer-dimer in the NTC
B) Nonspecific amplification in all samples
,C) Contamination of the master mix with genomic DNA
D) Incorrect probe hydrolysis
Correct Answer: A) Specific target amplification with primer-dimer in the
NTC
Rationale: A uniform peak at 82°C across samples indicates a specific amplicon.
The NTC peak at a lower Tm (78°C) is characteristic of primer-dimer, which melts
at a lower temperature due to shorter length and less GC content.
6. A technologist performing Sanger sequencing observes that all four dye-
terminator peaks in the electropherogram are extremely low in signal intensity, yet
the positive control sequence is perfect. The most likely issue is:
A) Excess template DNA in the sequencing reaction
B) Failed capillary injection due to a bubble
C) Degraded fluorescent dyes in the sequencing mix
D) Omission of the sequencing primer in the patient reaction
Correct Answer: D) Omission of the sequencing primer in the patient reaction
Rationale: Without a sequencing primer, chain extension cannot initiate, so no
labeled products enter the capillary. Positive control worked, ruling out dye
degradation or general machine failure. Excess template typically causes broad or
split peaks, not low signal.
7. Which of the following is an advantage of digital PCR (decry) over real-time
quantitative PCR (qPCR)?
A) Higher throughput for hundreds of targets per sample
B) Absolute quantification without a standard curve
C) Shorter run time for most assays
D) Ability to detect RNA without reverse transcription
Correct Answer: B) Absolute quantification without a standard curve
Rationale: decry partitions the sample into thousands of reactions; Poisson
statistics allow direct calculation of target copy number without a standard curve.
qPCR requires a standard curve for relative or absolute quantitation.
, 8. A molecular diagnostics laboratory receives a bone marrow specimen for JAK2
V617F mutation testing by allele-specific PCR. The run yields a visible band in
both the mutant and wild-type wells for all patient samples, but no bands in the no-
template controls. This pattern suggests:
A) The assay is working correctly for wild-type and mutant detection
B) All patients are heterozygous for the mutation
C) Nonspecific amplification due to excessive Mg²⁺ concentration
D) Contamination of master mix with wild-type control DNA
Correct Answer: C) Nonspecific amplification due to excessive Mg²⁺
concentration
Rationale: High Mg²⁺ can reduce allele-specific primer stringency, leading to
amplification in both allele-specific wells. NTCs are clean, excluding
contamination. All patients cannot be heterozygotes without positives and
negatives.
9. What is the function of uracil-DNA glycosylase (UNG) in a PCR reaction setup?
A) Degrade RNA contaminants
B) Prevent carryover contamination by digesting amplicons containing dot
C) Increase the annealing temperature for GC-rich targets
D) Remove secondary structures from single-stranded DNA
Correct Answer: B) Prevent carryover contamination by digesting amplicons
containing dot
Rationale: UNG hydrolyzes uracil-containing DNA. If dot replaces ditto in PCR,
previous amplicons contain uracil. Before the next PCR, UNG destroys these
contaminating amplicons, then is heat-inactivated during initial denaturation.
10. A next-generation sequencing run shows a high percentage of duplicate reads
(>60%) despite adequate library complexity. The most probable cause is:
A) Over cycling of the library amplification PCR
B) Insufficient fragmentation of genomic DNA
CERTIFICATION EXAM ACTUAL 2026/2027 COMPLETE APPROVED
QUESTIONS AND CORRECT DETAILED ANSWERS WITH
RATIONALES (100% CORRECT VERIFIED SOLUTIONS) NEWEST
UPDATED VERSION 2026 EDITION |GUARANTEED PASS A+ (BRAND
NEW!) |INSTANT PDF DOWNLOAD
1. A clinical laboratory is validating a new real-time PCR assay for Chlamydia
trachomatis. The technician runs a panel containing 20 known positives and 20
known negatives. Three positive samples yield no amplification, and two negative
samples show late amplification (Ct > 38). What is the diagnostic specificity of this
assay based on these results?
A) 85%
B) 90%
C) 95%
D) 100%
Correct Answer: B) 90%
Rationale: Specificity = True Negatives / (True Negatives + False Positives) ×
100. Here, true negatives = 20 total negatives minus 2 false positives = 18. So 18 /
20 = 0.90 or 90%. The false positives (late amplification) reduce specificity.
2. A molecular technologist observes that after each amplification cycle in a real-
time PCR run, the fluorescence signal increases but the Ct value for the positive
control is delayed by 4 cycles compared to the expected value. The most likely
cause is:
A) Incorrect annealing temperature
B) RNA contamination in the master mix
C) Reduced efficiency of the DNA polymerase
D) Excess template concentration
Correct Answer: C) Reduced efficiency of the DNA polymerase
Rationale: Delayed Ct indicates slower amplification kinetics. Reduced
polymerase efficiency (e.g., due to old enzyme, inhibitors, or suboptimal buffer)
directly increases Ct. Incorrect annealing usually causes no amplification or
nonspecific products. RNA contamination does not affect Ct of DNA targets.
Excess template would decrease Ct.
,3. Which of the following next-generation sequencing (NGS) library preparation
steps is responsible for attaching sample-specific barcodes to each DNA fragment?
A) Fragmentation
B) End repair
C) Adapter ligation
D) Size selection
Correct Answer: C) Adapter ligation
Rationale: During adapter ligation, sequencing adapters that include unique
barcode/index sequences are attached to both ends of fragmented DNA.
Fragmentation shears DNA, end repair creates blunt ends, and size selection
purifies fragments by length.
4. A patient specimen is received for HIV-1 viral load testing using reverse
transcription PCR (RT-PCR). The technologist forgets to add the reverse
transcriptase enzyme to the master mix. What will be the result?
A) No amplification because cDNA cannot be synthesized
B) Amplification will be normal because DNA polymerase substitutes for RT
C) Late amplification due to partial RNA degradation
D) Fluorescence signal only in the no-template control
Correct Answer: A) No amplification because cDNA cannot be synthesized
Rationale: RT-PCR requires reverse transcriptase to convert viral RNA to
complementary DNA (cDNA). Without RT, no cDNA is produced, and subsequent
PCR cannot amplify the RNA genome. DNA polymerase cannot use RNA as a
template.
5. In a melt curve analysis following SYBR Green real-time PCR, a single sharp
peak is observed at 82°C for all samples, but the no-template control shows a
smaller peak at 78°C. This indicates:
A) Specific target amplification with primer-dimer in the NTC
B) Nonspecific amplification in all samples
,C) Contamination of the master mix with genomic DNA
D) Incorrect probe hydrolysis
Correct Answer: A) Specific target amplification with primer-dimer in the
NTC
Rationale: A uniform peak at 82°C across samples indicates a specific amplicon.
The NTC peak at a lower Tm (78°C) is characteristic of primer-dimer, which melts
at a lower temperature due to shorter length and less GC content.
6. A technologist performing Sanger sequencing observes that all four dye-
terminator peaks in the electropherogram are extremely low in signal intensity, yet
the positive control sequence is perfect. The most likely issue is:
A) Excess template DNA in the sequencing reaction
B) Failed capillary injection due to a bubble
C) Degraded fluorescent dyes in the sequencing mix
D) Omission of the sequencing primer in the patient reaction
Correct Answer: D) Omission of the sequencing primer in the patient reaction
Rationale: Without a sequencing primer, chain extension cannot initiate, so no
labeled products enter the capillary. Positive control worked, ruling out dye
degradation or general machine failure. Excess template typically causes broad or
split peaks, not low signal.
7. Which of the following is an advantage of digital PCR (decry) over real-time
quantitative PCR (qPCR)?
A) Higher throughput for hundreds of targets per sample
B) Absolute quantification without a standard curve
C) Shorter run time for most assays
D) Ability to detect RNA without reverse transcription
Correct Answer: B) Absolute quantification without a standard curve
Rationale: decry partitions the sample into thousands of reactions; Poisson
statistics allow direct calculation of target copy number without a standard curve.
qPCR requires a standard curve for relative or absolute quantitation.
, 8. A molecular diagnostics laboratory receives a bone marrow specimen for JAK2
V617F mutation testing by allele-specific PCR. The run yields a visible band in
both the mutant and wild-type wells for all patient samples, but no bands in the no-
template controls. This pattern suggests:
A) The assay is working correctly for wild-type and mutant detection
B) All patients are heterozygous for the mutation
C) Nonspecific amplification due to excessive Mg²⁺ concentration
D) Contamination of master mix with wild-type control DNA
Correct Answer: C) Nonspecific amplification due to excessive Mg²⁺
concentration
Rationale: High Mg²⁺ can reduce allele-specific primer stringency, leading to
amplification in both allele-specific wells. NTCs are clean, excluding
contamination. All patients cannot be heterozygotes without positives and
negatives.
9. What is the function of uracil-DNA glycosylase (UNG) in a PCR reaction setup?
A) Degrade RNA contaminants
B) Prevent carryover contamination by digesting amplicons containing dot
C) Increase the annealing temperature for GC-rich targets
D) Remove secondary structures from single-stranded DNA
Correct Answer: B) Prevent carryover contamination by digesting amplicons
containing dot
Rationale: UNG hydrolyzes uracil-containing DNA. If dot replaces ditto in PCR,
previous amplicons contain uracil. Before the next PCR, UNG destroys these
contaminating amplicons, then is heat-inactivated during initial denaturation.
10. A next-generation sequencing run shows a high percentage of duplicate reads
(>60%) despite adequate library complexity. The most probable cause is:
A) Over cycling of the library amplification PCR
B) Insufficient fragmentation of genomic DNA
