ASCP BOC Specialist in Molecular Biology (SMB) Examination Practice Test
Molecular biology laboratory practice connects nucleic-acid integrity with reliable detection, amplification, and measurement of genetic targets. The available questions sample specimen handling for DNA and RNA, PCR chemistry, analytical sensitivity, real-time PCR quantification, droplet digital PCR, sequencing library preparation, and capillary electrophoresis.
Exam overview
About the ASCP BOC Specialist in Molecular Biology (SMB) Examination Exam
The question set also addresses how molecular scientists evaluate assay performance and distinguish technical failure from a true negative result. Topics include interpreting a real-time PCR standard-curve slope, understanding what a plasmid positive control demonstrates, and using digital partitioning to estimate target concentration without a calibration curve. Specimen selection matters when assessing constitutional variants, while pre-extraction handling can affect the quality of both DNA and RNA. Other items connect fluorescent labeling and fragment size to capillary electrophoresis, and examine how operator-to-operator variation can be recognized and reduced through laboratory quality practices. Together, these concepts support practical decisions in assay development, troubleshooting, nucleic-acid testing, and result interpretation.
Sample Practice Questions
Review a selection from this exam's published US Practice Tests practice bank.
A clinical laboratory is establishing a new molecular test and determines the lowest analyte concentration that can be detected reliably under defined conditions. Which performance characteristic is being assessed?
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Correct answer: AThe limit of detection is the lowest amount or concentration of an analyte that an assay can detect reliably under specified conditions. It is distinct from analytical specificity, which concerns discrimination of the intended target from other substances or sequences.
A molecular laboratory receives a tissue specimen intended for DNA and RNA testing. Which general handling choice best supports preservation of both nucleic-acid types before extraction?
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Correct answer: APrompt processing and validated preservation or storage conditions help limit nucleic-acid degradation. The appropriate condition depends on the specimen type and validated assay, so unvalidated treatments should be avoided.
During next-generation sequencing library preparation, what is the primary purpose of adding adapters to DNA fragments?
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Correct answer: AAdapters provide defined sequences that enable library fragments to interact with the sequencing platform and provide binding sites for sequencing primers. Depending on the workflow, adapters may also carry indexes, but they do not remove variation or ensure sample purity.
A DNA polymerase extends a primer during PCR. Which feature of the reaction supplies the chemical energy for nucleotide incorporation?
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Correct answer: AIncoming dNTPs carry high-energy phosphoanhydride bonds. Their incorporation releases pyrophosphate, and subsequent pyrophosphate hydrolysis helps drive DNA-chain synthesis.
A laboratory is comparing a patient’s germline sequence with a reference sequence. Which specimen is generally most appropriate for assessing constitutional variants when there is no concern about hematologic disease or recent allogeneic transplantation?
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Correct answer: AA buccal epithelial sample can provide nonhematopoietic human DNA suitable for constitutional variant assessment, provided collection and contamination controls are appropriate. Tumor-only and plasma specimens may contain acquired or mixed DNA and are not automatically equivalent to a germline source.
A laboratory is using droplet digital PCR to estimate the concentration of a target without relying on a calibration curve. Which principle supports the estimate?
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Correct answer: ADigital PCR partitions a sample into many small reactions. The fraction of negative partitions is used with Poisson statistics to estimate the number of target molecules, including correction for partitions that may contain more than one molecule.
A laboratory uses a plasmid containing a known insert as a positive control for an amplification assay. The control amplifies, but the clinical specimen does not. What does the positive-control result establish most directly?
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Correct answer: ASuccessful amplification of a positive control demonstrates that the tested reaction components and conditions can amplify that control target. It does not establish that a patient specimen contains target or is free of specimen-specific inhibition.
How to use this practice test
The free practice bank contains 50 published questions; each session presents up to 20 random questions. Use a session to test your understanding of molecular assay principles, then review the results to identify concepts that need closer attention, such as controls, quantification, or specimen handling.
Preparation tips
- For PCR questions, connect nucleotide incorporation to the reaction chemistry and distinguish amplification failure from inadequate template or inhibition.
- Practice interpreting real-time PCR standard curves, especially how slope relates to amplification efficiency, and contrast curve-based quantification with droplet digital PCR’s partitioning principle.
- Compare DNA and RNA preservation needs when reasoning through tissue handling, extraction preparation, and the suitability of a specimen for constitutional variant analysis.
- Review what positive and negative controls can establish in an amplification assay; a successful positive control does not by itself validate the clinical specimen result.
- Trace the purpose of sequencing adapters and fluorescent labels, then relate capillary electrophoresis separation to DNA fragment properties.