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Molecular Diagnostics Flashcards

6 cards from real ASCP 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 PCR, what is the role of the thermostable DNA polymerase (Taq polymerase)?

    Answer: To synthesize new DNA strands using primers as starting points

    Taq polymerase (from Thermus aquaticus) is a thermostable DNA polymerase that synthesizes new DNA strands by extending from the 3' end of primers using the template strand. Its heat stability allows repeated thermocycling.

  2. Southern blotting detects:

    Answer: DNA sequences

    Southern blotting (developed by Edwin Southern) detects specific DNA sequences. DNA is digested with restriction enzymes, separated by gel electrophoresis, transferred to a membrane, and hybridized with a labeled probe.

  3. A FISH break-apart probe is designed to:

    Answer: Detect gene rearrangements by showing split signals when a gene is disrupted

    Break-apart FISH probes flank a gene of interest with differently colored labels. In the normal state, signals are adjacent or fused. A chromosomal rearrangement splits the signals apart, indicating rearrangement regardless of the partner gene.

  4. Pharmacogenomic testing for CYP2D6 variants is clinically important because CYP2D6 metabolizes:

    Answer: A large number of drugs including codeine, tamoxifen, and many antidepressants

    CYP2D6 metabolizes approximately 25% of clinically used drugs, including codeine (to morphine), tamoxifen (to endoxifen), tricyclic antidepressants, SSRIs, and antipsychotics. Genetic variants create poor, intermediate, normal, rapid, and ultrarapid metabolizer phenotypes.

  5. Microsatellite instability (MSI) testing is most relevant for which condition?

    Answer: Lynch syndrome (hereditary nonpolyposis colorectal cancer)

    Lynch syndrome is caused by germline mutations in mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). Deficient MMR causes MSI — length changes in repetitive DNA sequences. MSI-H tumors in young patients prompt Lynch syndrome evaluation.

  6. In the CRISPR-Cas9 system, what is the function of the guide RNA (gRNA)?

    Answer: To direct the Cas9 nuclease to a specific DNA sequence via complementary base pairing

    The gRNA contains a approximately 20 nucleotide spacer sequence complementary to the target DNA. It directs Cas9 to the correct genomic location adjacent to a PAM (protospacer adjacent motif, 5'-NGG-3') sequence, where Cas9 creates a double-strand break.