AMT Molecular Diagnostics Technologist (MDT) Certification Examination Practice Test
Molecular diagnostics applies nucleic acid methods to detect and analyze genetic material in clinical specimens. This practice page’s questions sample PCR primer design, RNA reverse transcription, DNA quantification, extraction principles, and fluorescence-based detection, alongside specimen suitability and contamination control.
Exam overview
About the AMT Molecular Diagnostics Technologist (MDT) Certification Examination Exam
Molecular testing requires linking each workflow step to the quality and meaning of the result. Questions address primer orientation for amplification, the role of reverse transcriptase when RNA is the starting material, and how fluorescent dyes or hydrolysis probes generate real-time PCR signals. They also consider extraction choices when specimens contain proteins or cellular debris, and whether a transport medium is suitable for a particular assay. Control results are central to interpretation: amplification in a no-template control can indicate contamination, while a failed internal amplification control may make a target result unreliable because inhibition cannot be excluded. Practical decisions include separating pre- and post-amplification work, recognizing invalid runs, and distinguishing DNA concentration measurement by absorbance from dye-based fluorometry. These concepts connect assay chemistry with specimen integrity and defensible result reporting.
Sample Practice Questions
Review a selection from this exam's published US Practice Tests practice bank.
A DNA fragment is to be amplified by PCR. Which pair of primer orientations allows DNA polymerases to extend into the region between the primers?
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Correct answer: BPCR primers anneal to opposite strands flanking the region of interest. Their 3′ ends point toward one another because DNA polymerase extends from a primer's 3′ end, allowing the intervening sequence to be copied.
A laboratory receives a swab in a transport medium that has not been validated for a particular molecular assay. What should staff do before testing the specimen?
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Correct answer: BSpecimen type and transport medium can affect target stability, extraction, and amplification. Staff should verify acceptability against assay instructions and laboratory validation rather than assume compatibility or apply an unvalidated workaround.
A run's no-template control shows amplification in the target channel. What is the most appropriate general response?
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Correct answer: BAmplification in a no-template control can indicate contamination or nonspecific signal, depending on assay design and criteria. The laboratory should investigate and determine run validity using its established procedures rather than ignore or mathematically adjust the finding.
A laboratory uses a fluorometric assay to estimate double-stranded DNA concentration. Compared with absorbance measurement, what is a common advantage of a DNA-binding fluorescent dye?
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Correct answer: AMany fluorometric DNA assays use dyes that fluoresce strongly when bound to double-stranded DNA, providing a selective concentration estimate that can be less affected by RNA and free nucleotides than absorbance-based measurement. It does not establish sequence or functional suitability.
A laboratory is selecting a nucleic acid extraction approach for a specimen with a high concentration of proteins and cellular debris. Which general step helps separate nucleic acids from many of these contaminants?
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Correct answer: AMany extraction methods use selective binding of nucleic acids to silica or another solid phase. Wash steps remove proteins and other contaminants, and the nucleic acids are then eluted for downstream testing.
A real-time PCR assay produces a sigmoidal amplification curve for a specimen, but its internal amplification control fails to amplify. What is the most appropriate interpretation?
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Correct answer: BFailure of an internal amplification control can indicate inhibition, extraction failure, or another process problem. A target-like curve does not by itself resolve the control failure; interpretation and repeat testing should follow validated assay procedures.
A laboratory is handling amplified DNA products and preparing new reactions. Which practice most directly reduces the chance that amplified product will contaminate pre-amplification work areas?
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Correct answer: APhysical separation of pre- and post-amplification areas, with dedicated equipment and supplies, helps prevent carryover of abundant amplified DNA into reaction setup. This is a general contamination-control practice.
How to use this practice test
The free US Practice Tests bank contains 50 published practice questions; each session presents up to 20 randomly selected questions. Answer them as short workflow and result-interpretation cases, then use the displayed results to identify weak areas, such as control interpretation, PCR chemistry, or specimen handling.
Preparation tips
- Sketch primer direction on complementary DNA strands and verify that polymerase extension proceeds into the target region between primers.
- Compare the roles of reverse transcriptase, DNA polymerase, intercalating dyes, and hydrolysis probes in RNA-to-cDNA and real-time PCR workflows.
- For each control scenario, decide whether the run is valid, invalid, or requires investigation; distinguish target amplification from control failure and possible inhibition.
- Practice tracing extraction steps that separate nucleic acids from proteins and debris, and assess whether specimen transport conditions are validated for the assay.
- Map pre-amplification and post-amplification activities to separate work areas and identify handling practices that limit amplicon carryover.